I was playing Oblivion and I came across a book called, The Deathblow of Abernanit. I read the book and it seems to be about this place in Morrowind. The book seems to say that this Abernanit place was a stain upon the land. My question is this. What was Abernanit and what is the backstory to the place?

There are some annotations on the text here:
http://www.uesp.net/wiki/Morrowind:Death_Blow_of_Abernanit

There is a location called http://www.uesp.net/wiki/Morrowind:Abernanit in Morrowind, although the book was likely meant to be called The Death Blow of http://www.uesp.net/wiki/Morrowind:Ebernanit, which was a daedric shrine to Mehrunes Dagon.