We know that the potency of Void Termina’s mind hax (and that of characters who scale) is multi-galactic but I’m here to put a number on it.
First off we know that the Jamba Hearts scattered throughout the universe and we see here that at least 12 landed on Popstar alone (the other four shown are regular friend hearts) so it’s definitely a thorough scattering.
It’s important to note that we have yet to see an uninhabited land and creatures in this universe can live comfortably on any planet may it be normal, underwater, literally on fire, gaseous, undiscovered, I don’t even know, or Created moments earlier by a being who wants to kill everything, and despite that all the options creatures have moved onto man-made planets as well. So all planets are relevant for this calc and for simplicity I will be ignoring moons.
Now for the number of planets. It’s estimated that there is 100-200 billion galaxies each having about 160 billion planets.
Going for a conservative galaxy estimate 100 billion x 160 billion = 16 sextillion planets.
My estimate for the number of sentient creatures per planet is 20 trillion the approximate number of vertebrates (first paragraph adding marine and land vertebrates). I use this as the Kirby universe as far FAR more sentient species than earth and to be fair most species by this number are still not considered sentient.
Now not all the area on each planet is effected but we see in the opening cutscene linked above via the dark purple clouds that the area of effect a jamba heart has is about the size of Mt. Dedede and its surrounding peaks.
I’ll be going with a low estimate by using what is usually referred to as the worlds smallest mountain range Sutter Buttes said here to have an area of 75 square miles which according to this is equal to 194.25 square kilometers.
I used this as my comparison because both Sutter Buttes and Mt. Dedede have a similar visual structure and we know it should be a decent lowball as Sutter Buttes isn’t quite large enough to peak above the clouds (having a max peak of 610 meters while the lowest clouds hang at about 2,000 meters) unlike Mt. Dedede which is shown to peak slightly above the clouds here 45 seconds in.
As shown previously we see 16 hearts enter Popstar’s atmosphere and looking closer only 12 are the evil Jamba Hearts (the rest being friends hearts as stated before).
So we can multiply the area per planet effected by 12 to get 2331 square kilometers.
The earths surface area is about 510 million square kilometers.
510,000,000 / 2331 = 218,790.22 which is the number we need to reduce effected sentient life on each planet by from the total.
20 trillion / 218,790.22 = ~91,411,764.2 which is the number of sentient minds effected per planet.
91,411,764.2 x 16 sextillion = ~1.462e30 MINDS HAXED.
But because it seems Void Termina did not have all the Jamba Hearts put back into himself only having the vast majority so the characters wouldn’t quite scale to this.
So let’s remove a little bit over 10% of that number and call it an even 1.3 NONILLION.
For reference according to the article linked above that’s over a 4th of the estimated total number of individual bacteria on earth A.K.A. a lot.
Note on Popstar’s size:
Popstar is usually known to be larger than most planets however I have used Earth’s surface area regardless as it is hard to say how much larger it is supposed to be.
It should be noted that due to how flat Popstar is depicted to be it sharing a surface area with earth would already give it a larger diameter than it but let’s look at the alternative.
Using the diameter of Kepler-10c (usually referred to as the largest known rocky planet) of 30,000 km as a starting point I’ll try and find Popstar’s surface area as that of the area of a pentagon inscribed in a circle of said diameter multiplied by 2 for each side of the planet (this is honestly the best I have and the area of the pentagon not covered by Popstar’s height and width will go into its depth).
So a pentagon can be split into 5 triangles of equal size with the angle made at the center of the pentagon being 72 degrees.
The sides of the triangle that form that angle come from two adjacent vertices of the pentagon and meet at the center and would be equal in length to the radius of the circle it’s inscribed in.
The circle’s diameter is 30,000 km so the radius is 15,000 km.
Plugging the side angle side into this area calculator gives us an area of about 106,993,858 square kilometers.
106,993,858 x 5 = 534,969,290 square kilometers for our first pentagon.
534,969,290 x 2 = 1,069,938,580 square kilometers for our total surface area.
This is just over double Earth’s previously established surface area of 510,000,000 square kilometers.
Now despite the fact that this would just over half my previous numbers it wouldn’t really matter due to me using the lower bound for the estimated number of galaxies in the universe as using the upper bound would double it back to it’s previous position.
So because the final result is virtually the same with a low Popstar size estimate and a low galactic estimate as it would be with a high Popstar size estimate and a high galactic estimate there should be no need to change the final calculation.