The Sigil Keep is a Daedric tower in the Planes of Oblivion. And yeah, it comes from the game Oblivion btw. Perfect for adding this to your Nether world.

It's not exactly the same as a sigil keep, I was going to make it like a home/fort and adding beds but trying to be stick with the actual game. Its relatively empty, which means you can add floors to the spiral staircase and make it your home. I made this completely myself with no help from anyone and no programs included.

Enjoy and as always, have a nice day.