General Concepts in Tensei Shitara Slime Datta Ken (WN)

This will go over some general concepts in Tensei Shitara Slime Datta Ken.

Ultimate Skills

Ultimate Skills in tensei makes the user resistance to the abilities of skill below them.

This is brought up when Clayman thought his Unique Skill Puppeteer which attacks its targets soul and then completely controls them, was able to control Milim Nava. To which Gii Crimson basically laughs at the idea of a Unique Skill working on someone with an Ultimate Skill:

“	"That fool thought he could control Milim. It’s so impossible that it’s hilarious. There’s no way an insect like Clayman could do something that Guy never managed to do. Those who possess an ultimate skill are not affected by lower abilities. Every rule of the world is ultimately reduced to this unique level. In other words, they will not be affected by any form of magic–highest or not."	„
	~ Chapter 81

This is again reiterated in chapter 187:

“	"Magic doesn’t affect a person who possesses a Ultimate Skill. In a sense, this was the natural result because Ultimate Skills are of a higher rank of magic. But, it’s effective even if it only gives an indirect effect rather than a direct one. In other words, weakening magic and the like wouldn’t work, but giving support to an ally vanguard was effective."	„
	~ Chapter 187

And stated again in chapter 210

“	"Mizari was in the same situation as Leon, all her attacks were counterbalanced and she received damage from the excess energy. She seemed to begin to do some makeshift attacks, but everything was pinned down by Kazaream’s power. Naturally, all magic was nullified. That’s natural, since magic doesn’t work against Ultimate Skill."	„
	~ Chapter 210

So it's pretty obvious in this series that unless you have an ultimate skill, magic doesn't work on them, this gives them resistance to various abilities such as Soul Manipulation, Mind Manipulation, Matter Manipulation etc, as those abilities have been shown to be possessed by people who aren't ultimate skill users. Which makes sense as Ultimate Skill users understand the laws of the world and are thus superior in using magic than people who aren't Ultimate Skill Users:

“	"However, the ability is varied as it is called unique; that is, one of a kind. As it is unique, there is a great difference in the strength of the ability, if it becomes an Ultimate Skill, then there would be differences of power, like heaven and earth. The people who acquire an Ultimate Skill will come to understand the laws of the world. Therefore, they are existences that are superior in utilizing magic."	„
	~ Chapter 190

Additional ordinarily stealing an ultimate skill from its user is normally impossible as the skill is born from their soul and exists within it:

“	"Ordinarily, actually stealing an Ultimate Skill from its owner was impossible. For that Skill would be born from oneself, deep from one’s soul, and would be etched into their Nucleic Heart. The Ultimate Skill was truly personal, as opposed to Normal Skills beat into the body, or Unique Skills engraved into the outer crust of the soul."	„
	~ Chapter 185

Ultimate skills don't require an incantation:

“	And since ultimate skills do not require an incantation, merely wishing for something can produce results.	„
	~ Chapter 81

Ultimate Skill Users

Ultimate Skill Users can give fake info about themselves.

“	"When I tried to analyze him, I only obtained trivial information. He has the same wavelength of irregular Energy quantity;just like Diablo. In other words, His Energy level was high, but the data shows that he was a novice that’s not able to completely control his demonic aura. However, my eyes cannot be deceived. Or possibly, she may have deceived the analysis power of『Wisdom Lord Raphael』, this information was likely fake. To make the opponent see false information and misjudge his true power. This allows someone to grasp victory before a fight by having an opponent underestimate them. In my terms, it was to conceal power. In other words, it was for making it hard for an opponent to gauge your true power through suppressing your demonic aura. But this person’s idea was to exploit the opponent’s information analysis ability. Someone who’s made afraid by this kind of information was not worthy to be considered as an opponent."	„
	~ Chapter 80

Can conceal info about themselves

“	"And the one who tried to had a friendly talk with the girl was Dino. As expected. A completely KY-person. This man was fearless. But, he had enough power to back his attitude. He emitted a large amount of energy, but most likely he suppressed most of it. This one too, by using Jamming, he concealed his true ability."	„
	~ Chapter 80

Can know if they are being analyzed:

“	"If I try to analyze him seriously he would surely notice. What a shrewd guy."	„
	~ Chapter 80

Can't be analyzed by skills below their level:

“	"The Demon Lord Leon was before him. It was certain that this man was superior to him. Even with Yuuki’s ability, he was an opponent that couldn’t be read. With Yuuki’s ability, he could analyze a normal Unique Skill right away. If he couldn’t read it, then the opponent’s rank was higher than Unique Skill.	„
	~ Chapter 132

Turn Null

Turn Null is the energy that was used to create the world:

“	""The Ultimate and Supreme Ability――called『Turn Null』which produced the primordial energy needed to create a world. But in the end, it was impossible for him to recreate it. Even if he could recreate that ability, he would only cause the energy to go amok and disappear if he didn’t create a world like Veldanava did. After all, 『Turn Null』, as indicated by its name, was pure and super dense energy that destroyed everything. A super-tier level ability that allowed the destruction of the existing world and even the creation of a new world. It was said that Veldanava lost『Turn Null』after he created this world, and he was left with『Magic Essence Breeder Reactor』"	„
	~ Chapter 247

Mana Breeder Reactor

This allows the user to continuously create mana:

“	"It is said that Veldanava created this world and lost ‘Turn Null.’ And what remained after that was the ‘Mana Breeder Reactor.’ Veldanava was the most powerful because this ability allowed him to inexhaustibly create mana. And the ‘Mana Breeder Reactor’ was inherited by Milim, which made her the most powerful. Being able to control the concentrated mana that was stardust, was a by-product of the ‘Mana Breeder Reactor.’ "	„
	~ Chapter 247

Primative Magic

Primitive magic is the source of all magic, and can even affect those who have ultimate skills:

“	" I asked Ciel-san for more details, any kind of Primitive Magic was placed on a higher rank than the magic used by Demons. She said that it was the source of all magic. However, its characteristic wasn’t manipulating physical phenomenon, but the power to affect the soul. While it had no effect on physical matters, its effect was tremendous inside the spiritual world. In other words, it was a terrifying magic that could exert its effect while invalidating defensive barriers. I was surprised that it could even affect strong people who had awakened an Ultimate Skill. In addition, a being who could use this magic would become the natural enemy of any spiritual life-form. Just like how Ramiris easily got induced now, it could affect the inside of someone’s heart……"	„
	~ Chapter 246

Veldanava and the System of the World

Veldanava created several parallel worlds after being bored in nothingness:

“	"The world was cruel, but it granted you everything. That was the world that Veldanava had created. He, who was alone in the empty space, couldn’t bear the solitude. That was the reason why he created the world: in order to distract himself from the boredom. Then, just as Veldanava wished for, life was born in this world, and beings began to act freely and asserted their Wills. Finally, after a long time, humankind was born as a vessel for the soul with free will and high intellect. Veldanava was thrilled. For Veldanava, who had been bored with the world of emptiness, even just observing the activities of life was fun, but the activities of the creatures called human beings were even more stirring for him."	„
	~ Chapter 248

However humans began to war because of emotions, so he created a system to manage them:

“	"However, there was also a problem. Humans who acquired intellect stimulated each other and took unpredictable actions. If he left them unattended, they would immediately begin to fight against each other and would walk on the path of self-destruction. Several other worlds were born, but he could see that all of them had similar tendencies. Emotions were always the cause. Emotions were something that had been given to them and was necessary to give people the stimulus to develop even further, but emotions that had grown unchecked tended to reject the opinions of others. Different Ideas gave rise to various justices, Veldanava pondered. He decided to accept such phenomena were some necessary evils and the way of the world as a training ground for the soul. If humans were to be controlled completely, conflicts would disappear. However, they would lose the stimulus from emotions and the world would end up as a Dystopia, where people were all equal but without free will. Such a world was not what Veldanava desired. After that, he experimented many times and tried to develop humans into the direction that he hoped for. The conditions in many of the Parallel Worlds minutely deviated from one another, which led them to achieve different evolutions. Meanwhile, he carefully chose humans with matured souls and created Angels and Demons as the manager of the souls without a lifespan. He constructed a system so that the souls circulated to all dimensions. He restricted the managers so they wouldn’t cause excessive interference and appointed the role of the Observer so that the foundation of the world wouldn’t be destroyed. Those he appointed to be Observers were Guy, Ramiris, and Dino. I didn’t seem to be able to see anything spiritual because the little amount of magic essence in my former world, but perhaps that world might have an Observer, too. Oh well, not like that thing mattered to me now though. Anyway, the construction of the system was completed. The subjugation of the Giants and the likes that appeared irregularly was finished and the world had stabilized."	„
	~ Chapter 248

After the system was created, Veldanava fell in love, which caused an error in the system, thus the system decided to kill him:

“	"When all things began working smoothly, the Wheel of Fortune spun greatly. By meeting Lucia, Veldanava learned what love was. Then, they proved their love, and Lucia ended up pregnant with Milim. At that time, Veldanava lost all of his powers, but I could deduce that was probably due to the compelling force of the world. The reaction called Enforceability―― the constructed system had declared Lucia’s existence as harmful. From the system’s standpoint, God’s love must be poured out to everyone equally. However, Veldanava’s action of loving a specific individual seemed to have caused errors in the system. As a result, the price paid in order to repair the system failure was Veldanava and Lucia’s life."	„
	~ Chapter 248

The Soul and Core

The soul has multiple parts, the ego which is covered by the nucleic heart which is where all data is engraved, and the crystallization of energy around the nucleic heart forms the soul:

“	"Quality aside, flora and fauna had souls of very little energy. Compared to that, the amount in human souls was enormous. Whether this much energy was in any and all humans was not yet confirmed. Were they actually using this energy? It depended on their Skills, which used such Spirit Energy. Data engraved on the soul, would become one with the soul’s bearer. As for whether it was possible to input this data directly, it wasn’t so simple. First of all, there’s the ego, which is enveloped by the Nucleic Heart. It is there that all the data is engraved. The crystallization of energy around the Nucleic Heart forms into the soul. The Possession Jewel was a vessel on which this Heart was projected. The Heart didn’t possess its own energy, but the ego did. So it was possible to have an ego without necessarily having a strong enough soul to utilize Skills. And the Possession Jewel is able to use the Spirit Energy as a substitute for one’s internal reserve of energy. But that had its limits, considering that the quality of the energy being different. Well, it was a simple toy for enjoying the Labyrinth so the limits didn’t matter. The point is, even if the Nucleic Heart had Skill data engraved inside, without enough Spirit Energy, the Skills could not be used."	„
	~ Chapter 161

Nucleic Heart has been referred to simply as core on other occasions such as when Shion was revived from the dead:

“	"Shion’s soul, thanks to the blessing, has retained all her memories. Rimuru’s wish has taken form, and this blessing was bestowed. In addition to retaining all her memories, there’s an extra skill 『Complete Memory』. It is an ability that will allow the soul to return safely from the dead for an unlimited amount of times. With her soul and body establishing a connection once more, Shion’s core had begun beating once more. "	„
	~ Chapter 71

When Rimuru wanted to free Veldora from Rudra's Control:

“	"(Alright that’s enough, what matters is you’re alright. You *are* alright right?) ――Technically speaking, I’m fine. While destroying the Soul Corridor, I protected my Heart which served as the core. But because of that, I lost all control over my body, and had no means of recovering that control―― So that’s why. But as long as the core is intact, we have options available. (Wisdom Lord Raphael, is it possible to recover Ultimate Skill『Storm King Veldora』?) 《Alert. As long as the Nucleic Heart is intact, re-establishing the Soul Corridor is possible. There are no problems with the recovery of Ultimate Skill『Storm King Veldora』.》 Alright, problem solved. The remaining task would be to defeat Veldora’s “body”. It’s all good as long as we can recover the core."	„
	~ Chapter 174

When Veldora gained the ability to leave his core in Rimuru:

“	"Parallel Existence, kind of feels the most cheat-like. Leaving his heart(nucleic core) within my body, and creating a clone using Energy. That is now possible.…."	„
	~ Chapter 191

When Leon's core was damaged but his soul was intact:

“	"At a glance, his soul seemed intact, but his Core had taken damage. It was the source of power, that an awakened hero attained. If this was damaged, they became unable to properly control their powers."	„
	~ Chapter 214

The Nuclei Heart has already been established above to be where all the data is engraved, so obviously if it's damaged Leon wouldn't be able to use control his powers.

The soul also has 3 layers:

“	"Since coming to this world, she has discerned the three layers of souls. The soul–the source of power for humans and monsters. Cloaking themselves in their souls, the most brittle existence, the astral bodies Establishing themselves in power, spiritual bodies Those who have a direct connection to this world, material bodies The soul is the entity itself, there is no “being” outside of it. Any kind of consideration requires the presence of an astral body. Of course, should it be based on astral body alone, the being will dissipate into thin air. So a medium to record the memories is needed–spiritual body. However, spiritual body preserves kind of like virtual memory, hence cannot serve as a permanent medium. Hence the flesh. So for those with tempered souls, should they even sustain brain damage, recovery of certain memories becomes possible."	„
	~ Chapter 66

Spiritual Lifeforms

Spiritual life forms don't have physical bodies, Benimaru when he became one lost his physical body:

“	"Looks like he managed to get along with Momiji, and has safely ascended. Discarding his physical body, he had fully evolved into a Spiritual Life Form. Albeit lower than the True Dragons, he is still an Elemental Divine Spirit nonetheless. "	„
	~ Chapter 191

Zegion as a spiritual life form has a body composed of water:

“	"Oops, seems I didn't notice until Ciel told me, but Zegion is also an Upper tier Spiritual Life Form now. He is a splendid Water elemental Spiritual Life Form. So does that mean that his body is composed of condensed water molecules collected from the surrounding atmosphere? Well, they do say Hihiirokane is an illusionary metal that has a lot of condensed Energy. He is still using the Adamantite exoskeleton preciously, it seems. If it wasn't something that I gave to him, he would probably have discarded it and became a fully fledged Spiritual Life Form."	„
	~ Chapter 191

Leon became the holy aura within him when he became a spiritual life form:

“	"An analysis shows, that he has become a Demi-God. Before this Leon had generous amounts of holy aura inside of him, now he has become the very holy aura that used to be within him. Simply said, he has become a spiritual entity. "	„
	~ Chapter 214

Spiritual lifeforms can survive physical death:

“	"「We see, she may be dead, but she may live again」 Ruminas pronounced her judgment after looking at the girl. This girl still has her soul. Two souls to be exact. 「Really?! Sis is alive?!」 「Nay, she is not alive. Nor is she dead. Death is but a state of the body; true death is the vanquishing of the soul. This girl still has her soul. So she is not dead」 「But this is strange. Why did her soul not disappear upon death?」 Normally, a soul disappears when its vessel is destroyed. Beings like I can survive death of the flesh, but normal monsters and people are different."	„
	~ Chapter 135

High ranked spiritual lifeforms can move in stopped time:

“	"Even in the world where the time stopped, Chloe could move calmly. In a world where normal eyesight didn’t have any meaning as even the light particles have stopped. In this world where time stopped, the reactions from the energy released is used to perceive the situation. Whether it’s Heroes or Devils, since they were bound by the world’s rule, it’s impossible for them to act. However, Chloe had transcended that restriction. In other words ――  (This person, was a spiritual lifeform too, that’s it)"	„
	~ Chapter 191

Spiritual lifeforms don't have a lifespan:

“	"It seems, procreation becomes impossible after evolving from an Ogre to a Demon Lord. Because the concept of life span would disappear, the ability to make a child does not seem necessary."	„
	~ Chapter 162

Spiritual lifeforms are immortal and can't die unless their core is destroyed, which has already established to be within their souls:

“	"Turn a body of flesh into that of a Spirit Form for a certain amount of time’ That was the hidden power of God-tier armour.A Spirit Form, in other words, a God-like Being. Veldora was like that, and speaking of which, I was too. I didn’t pay much attention, but it was certainly a state close to being immortal. Eternal youth was guaranteed, along with a strong degree of immortality. I couldn’t die unless there was a Core Break or Energy Roast successfully performed on me. Although temporary, to be able to grant an existence of that scale, this armour was fearsome.But for this reason, it was not suited to half-Spirit Forms like Benimaru, and even less for true Spirit Forms like Demons.The armour had gone to where it belonged"	„
	~ Chapter 164

Spiritual lifeforms can regenerate their cores as long as they are not destroyed, and again cores have already been established to be within their souls.

“	"Leon who is one of the Octagram was on the verge of being killed now. In case of Mizari who is a spiritual lifeform, her core would be likely to be able to regenerate as long as it was not destroyed. However, Leon is a high ranking human who possess holy body. He was an awakened Hero, which was similar to existence which don’t have lifespan but―― certainly it was depending on the physical body. If he evolves to be a spiritual lifeform and become a demi god, the matter might have been different.	„
	~ Chapter 164

So what does this mean? Spiritual life forms have eternal youth and unless you destroyed their cores within their souls, will regenerate.

Infinite Prison

Chloe O’Bell used infinite prison to seal Veldora Tempest, this sealed him in imaginary space:

“	"The Hero’s Unique Skill『Infinite Prison』is a skill which sealed the target for an eternity in an imaginary infinite space; an unpleasant skill that does not allow interference to the real world."	„
	~ Chapter 4

Soul Corridor

In order to escape Infinite Prion, the Soul Corridor was developed. Soul Corridor allows the user to be immortal as long as someone else exists:

“	"A “Soul Corridor”, huh. So all my memories will transcend time and space and are accumulated within you. So, in other words, as long as you exist, I am immortal. Even if I am again sealed in an Infinite Prison, all you have to do is to cancel the summon. I mean, I always was nearly invincible, but now I’m immortal as well…」"	„
	~ Chapter 74

This allows Rimuru to be immortal as long as one of his clones exist:

“	"After all, it’s because the new ability Ciel had created, 『Multiple Existence』was incorporated into Ultimate Skill『Void God Azathoth』. It was an ability Ciel made after she finished analyzing Ultimate Skill『Evil Dragon Azi Dahaka』, I could create clones which all connected with this ability. Thanks to this ability, I didn’t need to be cautious of Velda anymore. Thus I revealed myself, but I think that it was still impossible, even for Velda, to sense me in this subspace. Still, I shouldn't carelessly rule out the worst case scenario. However, there’s no problem for now. Even if he sensed me and isolated Ramiris’ labyrinth, my clone which can also called as my main body still exists in the Imaginary Space. If Velda did isolate the labyrinth, there’s a possibility that the connection with the main body will be cut off, but it will be easy to ascertain that if both sides detect each other. After all, both are me. It’s a weird sensation, but Parallel Thought works without much difficulty, so there’s no problem even when doing different actions. It wasn’t a half-baked version like the one Vega used. It could be said that since Ciel had completed this『Multiple Existence』ability, destroying me would be a nigh impossible task. Each of my『Multiple Existence』were connected through the “Soul Corridor”."	„
	~ Chapter 233

Spirits

The holy spirit is the source of power, that first existed and gave birth to spirits of light and darkness which came into existence the same time as the world. From them, the spirit of time and the other spirits were born:

“	"A spirit is… “In nothingness power finds its fill. That is a holy spirit. The great holy spirit is the source of power. Among these, light and darkness, the two great spirits. Who came to exist at the same moment as the world. But, the world was without form, a ephemeral existence. Light and shadow, darkness and the light. Two existences that shall never interweave. One day, the great spirit time was born. The child of light and darkness. And thus the world began to move. The moving world spun, without purpose, around itself. Inside the flowing currents of life and death, Earth, Water, Fire, Wind, and Sky–these five great spirits were born. And since then, these were the great eight spirits. Until the light consumes the world, erasing darkness. Until a new spirit is born, erasing all. Life and death, heralding the coming end of the world.	„
	~ Chapter 62

The spirits are masses of energy:

“	"「In other words, first the holy spirit had existed, and it gave birth to the other eight!」 Splendid… right? For a myth, it surprisingly lacks gods. Perhaps this is the truth of this world. By the way, great spirits did not have ego–they were masses of energy.	„
	~ Chapter 62

Demons and Angels

Demons can manipulate minds:

“	"Arnaud suddenly realized. There was a characteristic of monsters that were Demon-kin called the Temptation skill. To mesmerize the target. An ability that can manipulate someone’s mind as it likes. But, he’d never heard of a Demon that had the ability to mesmerize a Holy Knight. To save someone under this mesmerization you either have to defeat the demon who is manipulating them… or kill the person."	„
	~ Chapter 90

Demons can teleport:

“	"Karion was startled for a moment, but then regained his calm and used magic perception to observe his surrounding. High ranked devils are those who mastered transfer magic. Pulling it off instantly and without a chant was unexpected, but nothing that can’t be dealt with. In the space-time category of abilities, Transfer consumed the most magical energy. Creating a gate and stabilizing space is the safest, and consumes the least magical energy to move. However, what Diablo did just now–transferring without the use of a gate, even when moving by himself–was ten times as costly. And to teleport without the use of a chant… only a handful of high ranked devils could do that. This isn’t an ability usable by just anyone. And the teleportation ability just now, it’s an advanced ability above spatial transfer. Spatial transfer may look instantaneous to the average person, but in the eyes of a master there’s a slight time lag. However teleportation happens literally in an instant, time lag doesn’t occur. It is the pinnacle of the transfer type abilities."	„
	~ Chapter 109

Demons exists as a mass of energy:

“	"From the bottom of my body, I could feel a power gushing forth. I seemed to exist as a mass of energy. As in this darkness full of saturated energy, energy that overflowed from my body might not leak out. How could I explain it so that it’s easy to understand? I couldn’t explain it well because I didn’t have the knowledge, but it was like crystallized sugar inside sugared water, I think that our existences were like that."	„
	~ Intermission:Venom's Story

As spiritual lifeforms demons can regenerate:

“	"The Demon was unruly, it was trampling the demonic territory. In the underworld, or as it was sometimes called, hell, in this spiritual world it defeated strong demons just like the incarnation of violence. The powerless ones had long fled, and those with strength had banded together to fight it head on. But for that Demon, the grief of the weak and worthless could not be heard. That Demon completely destroyed its opponents, and continued to trample them calmly. Demons were a spiritual life form. Therefore, even if their bodies were destroyed, they would revive themselves through self-regeneration over time. Maybe knowing this, that Demon didn’t restrain itself and did not give mercy to those who came."	„
	~ Chapter 143

Demons have no physical bodies in the underworld and receive power from the spirit of darkness:

“	"This world was the Underworld. In other words, this world could also be called Hell. It was the Spiritual World, the home of demons that didn’t possess a physical body. I was inside such world. I seemed to be a Lesser Demon. Demons are an existence like spirits or angels. It seemed to be an existence that received receives power from the spirit of Darkness, and specialized in the demonic attribute. Similarly, the Angel specialized in the holy attribute of the spirit of Light, the exception to this seemed to be called a Spirit."	„
	~ Intermission:Venom's Story

Demons also don't have souls and only gain a soul when summoned into the material world:

“	"Summoning.It means to be summoned to the material world from the spiritual world. By obtaining a temporary body, the pleasures of the surface could be tasted. That is smell, touch and taste. I could collect enough information to control the world. A summoned demon without an ego seems to be affected by the personality of the Summoning master. Various kind of information is received from the summoner’s side. According to the contents of the request, it seemed that I could obtain a lump of information called “Soul”.*We could evolve into higher beings if we collected a lot of “Souls”."	„
	~ Intermission:Venom's Story

Demons are also said to have been born conceptual existences:

“	"At the same time when Spirit of Time was born, the egg hatched, and the seed budded. The two were born as a conceptual existence with a pure energy body without a physical body. That was the origin of Angels and Demons. The mysterious thing was that the Angels and Demons that were born at the same time were on bad terms."	„
	~ Chapter 114

Demons can resurrect:

“	"To Testarossa, death isn’t something to be feared. In a few hundred or at most a thousand years, it is possible for her to revive with some of her memories and personality. However, when she thinks that there might not be any of her allies left till then, she can’t help but feel sad…"	„
	~ Chapter 240

Stated again to able to resurrect:

“	"With Velgrynd’s confirmation, Guy decided to put his trust in both of them. Even if she lost and he died, he would still be able to revive in a few hundred years at the worst."	„
	~ Chapter 235

Demons are on the same level as spirits:

“	"Its existence can be called as such: Arch Demon. A resident in the spirit world as well as to the physical world where humans reside, it is an existence above devils. It is a spirit being, unmoved by the forces of this world unless reincarnated. Essentially, they are on the same level as spirits. When summoned with magical energy, all it could do is obtain a temporary physical body and function for a short duration. However, there are also those who gain a physical body in the physical world."	„
	~ Chapter 71

Arch Demon

Arch Demons are capable of destroying towns:

“	"Their strength, “A+”, is said to be equivalent to pre-demon lord class. And their powers, remained as demon lords of legends. A single devil who destroys untold numbers of towns. In both name and reality, it is said to be the strongest of the demon lords. Such a being with the caliber of a demon lord, the Arch Demon is right in front of his very eyes."	„
	~ Chapter 71

Arch demons are also stated to be comparable to tactical nukes:

“	"「If you think about it, normally you would think that the guardians that protected the research facilities were strong, right? But, the people that belong to that country’s army are monsters, right? If so, the guardians in the labyrinth aren’t the strongest, right?」 「I think the same. At least, the Demon Lord Rimuru might be an exception. In the past, a city seemed to have been annihilated by a wicked dragon named Veldora… Actually, a similar thing seemed to have happened. I think that an Arc Demon is equal to a tactical nuclear weapon in Earth.」"	„
	~ Chapter 147

True Dragons

True Dragons are spiritual lifeforms:

“	"(Hmm. Actually, I don’t need a core… the secret you ask? Because I'm a “Perfect Individual”. A special being. As I’m a spiritual life-form, I have no fixation to physical body. This physical body was only a response to the belief of the surroundings.)"	„
	~ Chapter 4

True Dragons exist only as souls:

“	"And, there are monsters who live with only a soul. That kind of being, however, is inferior to the rest. But, even if it is but a soul, should it obtain some level of intelligence, it will be recognized as a monster. These are what the world knows as the four dragons, the highest form of being.	„
	~ Chapter 66

True Dragons can resurrect:

“	"(Is what he said. If only mind that escape out, it seemed that it’d diffuses with magic essence and disappears. And then, somewhere else, a new “Storm Dragon” would be born. It might be possible to escape, but if there’s no meaning to it if it he became a different person."	„
	~ Chapter 4

Stated again:

“	"What do I need to do for Milim to forgive me”――While I was thinking about such thing, I heard Ciel’s calm voice. “Huh? What are you saying, Ciel?” I questioned, but it can’t be helped It’s like I had led Gaia to suicide, it would be something that Milim will never forgive me for even if it was unintentional. I didn’t really mean it when I said that Gaia can become a real “True Dragon”…… Ehh, it can’t be!? At the same time that I thought of the possibility, the “Dragon Core” conspicuously glowed and flickered at the center of the tetrahedron. 《You’re aware that a True Dragon won’t really disappear, right? The same also applies to Zero who had become the insane, destructive “Berserk Evil Dragon”. He will revive again somewhere in the world and will just try to accomplish his mission as the “Berserk Evil Dragon” that was given to him by Velda."	„
	~ Chapter 233

Food Chain

The reason why Rimuru is so powerful, in short he can gain all his subordinates abilities:

“	"Food Chain: It is now possible to acquire skills from your subordinates (※ All of them)"	„
	~ Chapter 41

In addition, Rimuru is always getting stronger:

“	"Moreover, Rimuru’s current circumstances were important to consider. The evolutions of his subordinates were now proceeding much faster. Every one of them who were bonded to Rimuru by the soul, was granting power to him through 『Food Chain』. As more time passed, Rimuru’s power only kept growing larger. Wisdom Lord Raphael, who maintained and ensured optimum usage of power, was now acting a support system for an all out assault. Accordingly, he converted all the abilities received from the subordinates into Energy, and provided it to Rimuru. "	„
	~ Chapter 173

This makes people who were previous threats to him, inferior:

“	"Was this him going all out? It was almost too stupid to be true, I think, and reject the thought. When I had met Velda at the imperial capital, I sensed a presence that was almost horrifying. I still believe that I would have been completely outmatched had I fought him at that time. And yet, the person who was here did not feel like a threat in the same way that he did before…   [Of course, he doesn’t. You have evolved every single day, master.]"	„
	~ Chapter 245

Ciel

A skill that is apart of his soul that is made for analysis:

“	"WAt my thoughtless whim, Ciel, the intelligent interface, had separated herself from Wisdom Lord Raphael. Her official title seems to be Manas (Divine Wisdom Core); An intelligent core, she can be thought of as that sort of thing. Similar to a Spiritual Life Form, she is incapable of materializing by her will alone. An entity that only “thinks”; She has become that sort of existence. Existing as a part of my soul, one can think of it like having a second “heart” (Strictly speaking that’s not the case, cognition being ‘sense of self’ = heart)."	„
	~ Chapter 191

Ciel was able to synthesize the abilities stored in food chain which granted Rimuru new abilities, which allows him to do various things including creating new skills:

“	"Secondly, what looked like the pot that received the remaining skills, was[Harvest Lord Shub Niggurath]. This was simply, a skill made for my followers. Skill Creation… Information that has been gathered by[Food Chain]and[Analysis], are used to create new skills. Skill Duplication… The ability to make copies of obtained skills. Skill Gifting… The ability to grant the copied skills onto the target. Can also remove the granted skills. Skill Bank… Turns skills that have been obtained into information and stores them, able to reproduce the skills at any time. Turning the hefty amount of skills that have been consumed into information, it’s now all stored nicely. Plus, they can be reproduced whenever. Now that is one absurd ability. Granting a Gift to my followers, has also become possible. But regarding that, there was compatibility of the follower etc. to consider.	„
	~ Chapter 191

Ciel can even conceal the voice of the world, this is the same voice of the world that shows up every time someone gains a new skill or evolves, and as already explained above, it is the system that was set up by Veldanava to manage the souls of all dimensions:

“	"At the same time, various pieces of information begins to flow into me, and became a torrent. 《Notification. Manas (God’s Wisdom Core): Ciel was born from Ultimate Skill[Wisdom Lord Raphael]. This announcement was concealed by Manas: Ciel.》 Suddenly, the “Voice of the World” had reached my mind. This is…… an evolution? Raphael-sensei, no Ciel-sensei seemed to be able to hide it in concealment mode. Ciel seemed to able to conceal even the “Voice of the World”. I’m amazed. .	„
	~ Chapter 190

Information King: Akashic Records

Yuuki Kagurazaka spent 1 month analyzing every ability in the series, and was able to use almost all of them except Rimuru's Turn Null and Milim's Mana Breeder Reactor

“	" However, Yuuki didn’t feel any anger regarding that matter. On the contrary, Yuuki wanted to show his respect towards Rimuru’s brilliant skills. Yuuki made the decision to move personally for the first time when the situation on the board titled so much that he couldn’t win, even if he unleashed all of the pieces in his hands. It wasn’t like when he was playing around during his fight with Leon. Yuuki seriously decided, for the very first time in his life, that he wanted strength. He estimated that it would take one month for him to unravel all that power. Meanwhile, he decided to let Velda be in the firing line and do as he pleased. Although Yuuki’s personality was more or less positioned at the top of the pecking order, because it was a mutual switch of beings of the same rank, once they switched places, he couldn’t switch with Velda with just his own Will. For this reason, this was a gamble for him. Velda’s goal was also the collapse of the world, but the end result was different than Yuuki’s. Yuuki’s end goal was to return this world to nothingness, but Velda’s was different. After the collapse, Velda wanted to try to create a new world with him as its God. From Yuuki’s point of view, that was a naïve idea that he couldn’t hold back his laughter when thinking about it. While thinking that Velda would fail anyway, Yuuki gave his last order. Thus, the result was as Yuuki had expected…… Yuuki was a genius, but he didn’t obtain all of Veldanava’s powers. As such, being able to control all of Veldanava’s powers was a lie. However, there was nothing that worried him. Because it was true that he could use almost all of Veldanava’s abilities. Yuuki already had enough power to destroy this world. The Manas called Velda had the knowledge about all of the Ultimate Skills, but he didn’t have the ability to recreate them. The reason was plain and simple, insufficient capacity. Yuuki had analyzed every skill over a month’s time and made a selection. He reduced Ultimate Skill『Greedy Lord Mammon』into energy (Existence Value) and tried to recreate the necessary skills. It became possible for him to perfectly recreate『Creation Lord Ahura Mazda』. However, there was also an ability that he couldn’t recreate no matter how hard he tried. The Ultimate and Supreme Ability――called『Turn Null』which produced the primordial energy needed to create a world. But in the end, it was impossible for him to recreate it. Even if he could recreate that ability, he would only cause the energy to go amok and disappear if he didn’t create a world like Veldanava did. After all, 『Turn Null』, as indicated by its name, was pure and super dense energy that destroyed everything. A super-tier level ability that allowed the destruction of the existing world and even the creation of a new world. It was said that Veldanava lost『Turn Null』after he created this world, and he was left with『Magic Essence Breeder Reactor』. Veldanava was the strongest existence because of this ability, which produced unlimited magic essence. Milim inherited that『Magic Essence Breeder Reactor』, making her the strongest. It was due to the byproduct of『Magic Essence Breeder Reactor』that she could control Stardust, the condensed form of magic essence. Yuuki had recreated this ultimate power too. Yuuki became a God-Man and a spiritual life-form. Therefore, based on Velda’s knowledge, he created『Magic Essence Breeder Reactor』and completely controlled it. However, as it was, he didn’t have enough capacity to use other abilities and became nothing but a rehash of Milim. He could control the output like Guy, but then he wouldn’t be able to surpass them. Yuuki thought as such, so he came up with the idea of recreating the abilities and put them inside Veldanava Sword. Veldanava Sword was a crystallization of Veldanava’s powers. It was the condensed form of half of Veldanava’s maximum energy. Milim was supposed to inherit this Sword of God someday. Hence, such a thing as recreating the abilities in Velda’s memories was easy. Yuuki had also disassembled his own Ultimate Skill『Creation Lord Ahura Mazda』and combined it with Velda’s knowledge. Thus, Origin Skill[2]『Information Ruler Akashic Records[3]』was created. He installed this Origin Skill into Veldanava Sword and tweaked it so that any selected ability could be used at any time. Because it was tuned exclusively for Yuuki’s use, it couldn’t be used by Velda. Velda’s role was to keep『Magic Essence Breeder Reactor』always in the optimal state, acting as a kind of permanent monitoring device. Thus, Yuuki was reborn as an incarnation of absolute power that could freely use all abilities.	„
	~ Chapter 247

Why is this important? Because despite all those abilities Yuuki had to concoct an elaborate plan to send Rimuru to the end of space-time.

Yuuki says Rimuru is equal to him:

“	" Yuuki was only wary of one person. Only against Rimuru, who had a dumbfounded expression in front of him. This annoying monster always exceeded Yuuki’s assumptions. For this reason, there was no need for him to hold back. As soon as he determined the extent of Rimuru’s capabilities, Yuuki would need to use his strongest technique to get rid of him. They were equal in power. Yuuki, who was a God-man and an Awakened Hero, was operating『Magic Essence Breeder Reactor』at its maximum output, and yet he couldn’t surpass Rimuru’s power. This was abnormal. (This is so troublesome, seriously. I had thought that I would surpass him with a bit more power, but――) Yuuki was advantageous in weapon’s performance, but he didn’t know how things would turn out if the fight dragged on.	„
	~ Chapter 247

Yuuki despite all the abilities he had, was forced to use his trump card

“	" Just as he expected, Rimuru seemed to be unable to predict this attack. Yuuki continuously manifested phenomena by merely thinking of them. Cornering him with flames, sealing his movement by hardening the ground, severing the space―― Rimuru was toyed around with by Yuuki. This was his last resort. One of the trump cards that he thought surely would be effective. However, unfortunately, Yuuki concluded that this Primitive Magic couldn’t defeat Rimuru. Naturally, there was a very deep and calculated reason for why Yuuki used Primitive Magic despite it not being able to deal the decisive blow. Yuuki judged that Rimuru had a habit of constantly observing his opponent’s attacks. It probably was a sign of his confidence that he could deal with any kind of attacks, but there was more than that. Yuuki thought that came from Rimuru’s innate naivety as he wished to find out his enemy’s true intentions and whether they could reach a mutual understanding or not. This time, Yuuki made use of that habit. As he expected, Rimuru didn’t use his full power from the start so Yuuki succeeded in activating Suspended World. If he used Primitive Magic in this stopped time, Rimuru would very likely start to analyze his actions. Although Primitive Magic was Yuuki’s trump card, he couldn’t beat Rimuru with it.	„
	~ Chapter 247

Which is proven when Rimuru quickly copies and nullify's Yuuki's abilities:

“	" Just as Yuuki planned, Rimuru seemed to be analyzing the Primitive Magic. Analyzing your foe’s hands while in a fight couldn’t be said to be wrong. However, being preoccupied with something trivial during a tight battle like the one Yuuki and Rimuru were currently in was a bad move. Yuuki had done various preparations since this battle began――No, even before it started. Naturally, while he was analyzing abilities inside Velda, Yuuki had always been formulating plans on how he would eliminate his strongest rival. Even stopping time wasn’t just for making himself have the upper hand by restricting Rimuru’s abilities. Rather, Yuuki’s aim was to make Rimuru think that. His true aim of using Time Stop wasn’t for such an insignificant reason―― 「How naïve, Yuuki. I gradually got the hang of it, don’t think that you’re the only one who can use magic while time is stopped!」 As Yuuki had expected, no, even faster than expected, Rimuru seemed to have completed the analysis of the Primitive Magic. The primordial flames that Yuuki had invoked without chanting were frozen by Rimuru just now. Yuuki’s Will was offset by the conflict between fire and ice. Yuuki thought that he had no choice but to smile wryly about this. One of his trump cards was nullified so quickly, even though time was stopped. However, even this was as Yuuki planned. The katana clashed against the sword. Both sides fought with their sublime powers. In this situation, Yuuki had succeeded in distracting Rimuru’s consciousness even if it was just for a moment. ――I’ve been waiting for this moment!!―― Yuuki smiled. Then, as he clashed with Rimuru with all his power once again, Yuuki put the final phase of his plan into motion. While enormous amounts of energy clashed against each other and spread shock waves, Yuuki activated a magic spell formulation without chanting. Naturally Rimuru, who had understood Primitive Magic, activated his own magic to deal with Yuuki’s magic and nullified it.	„
	~ Chapter 247

Also as mentioned above Velda specializes in all ultimate skills, it just did not have the ability to replicate them, it was revealed previous that Velda was originally the skill of Veldanava, which means Veldanava had the ability to use all abilities, and Rimuru>Veldanava, plus Rimuru absorbed Yuuki and Velda was apart of Yuuki's soul, just like Ciel is apart of Rimuru's.