Using your mod with Masterwork, some of your creatures are making their Succubus pet-adding scripts freak out (which stopped when I deactivated succubi), and also making the dfhack exportlegends script crash (before and after I deactivated Succubi), and try as I might I cannot figure out why. I don't really care about the wellbeing of the succubi, but the exportlegends not working is a bit pesky.
I split your creatures into separate files to see who was responsible, and it is the Drider, the Drow Spider, the Giant Drow Spider, and, heartbreakingly, the Rothe.
The Drow themselves, the Quaggoth, and the Riding Lizards are fine.
The error messages aren't super helpful, talking about not being able to read "Cannot read field vector<caste_raw>.1:index out of bounds." but after experimentation with swapping Llama caste section into the Rothe, I'm not convinced it's actually the caste data that's at fault.
At any rate, it's all a bit above my paygrade, and I hope someone more knowledgeable can solve the mystery.
Edit: OK, that mystery was in fact incredibly obvious. Meph had added some of Rhenaya's creatures to Masterwork, and kept the same IDs which presumably was confusing the heck out of all manner of things.
@Bernard2012 From my investigations through the Drow mod files, trying to solve my issues, I am almost certain that it does not turn unicorns into thieves. Was it maybe being used as a mount by a thief? I've never seen a mounted thief, and it seems counter-productive for sneaking, but could be possible. No idea why it crashed you.