I think he is mountain level based on how he shaked the entire Dwemer city of Irkthand to collapse a giant skycrapper-size tower and divert flow of river into the cave. I noticed in the past, Karliah said that Nightingale HQ in Riften was carved/atomized by the first Nightingales with their powers. Of course, Mercer Frey is way above their league.
Why'd you delete the planeswalker page? Azathoth and I weren't sure about it at first, but it was seemingly decided in the deletion thread a while back that the page.could stay and that stats issues and such would just go through a normal CRT.