Here's the mod. The Chosen of Cyric encounter was especially nice.
But if you want this mod, I'd have to warn ye.
The Shadow Thieves Improvements component is to be taken at your own peril! I did EVERY quest possible before doing missions for the vampires, and you just can't believe how powerful the thieves still were! With my lvl 15-20 party, it took about 10 tries to clear the thieves from the gates of the Shadow Thieves' compound!
Anyone else tried this mod?