So I came to the college of winterhold (I am the arch mage) to try to buy some spellbooks off of Faralda. At the time I had 2 Ascendant Necromancers thralls, and all of the sudden when I entered Hall of Countenance to buy some spellbooks she immediately turn hostile towards me. Of course it set off my slaves to start attacking Faralda to defend their master

Anyhow I don't remember having any bounties over my head, but what ended this mess was when I enter the paycrimegold code. She no longer attacked me.

What the heck happen?

Seems pretty selt explanatory, don't you think -- Necromancy is a serious crime.

I don't see it as a serious crime if you use it for good. My 2 slaves were bad guys at the time

I've had at least 50 different thralls follow me all over the college and that has never happened to me, so I doubt that's the case.