Hmm. I thought it needed the Daedric Smithing Perk?
Surprisingly not.
Perfect for a fallen hero storyarc for those of you tired of your righteous hero characters.
After, with the best of intentions, defeating Miraak, your character is in servitude to Herma-Mora (whether he knows it or not) and slowly descends to darkness, going from revered hero to the thing that people tell their children about to keep them inside at night, slowly becoming an old legend along the lines of the Headless Horseman and the Grim Reaper.
Yeah, that's what happened to my character, actually. He was a righteous guy, telling Hermaeus Mora to piss off from Discerning the Transmundane up until he defeated Miraak. But then he started using Miraak's equipment (Mask, Clothes, Sword, Staff) and slowly became to be subtly influenced by it to become a devout follower of Hermaeus Mora.
I just can't wait for the PC version to come out so I can fix Miraak's stuff. You can't upgrade any of his apparel, and his mask and sword enchantments are just laughable.