There are 2 doors that make some of the druids and tiefling hostile after being used. I have tested using only 1 door at a time and if either are used, and does not have to be both, will cause Nettie, Eramas, Arron, and Findal to become hostile. There may be more NPC's that go hostile, but didn't run into them. The door in the Enclave Library that requires the Key of the Ancients headpiece, and the door in the Underground Passage that leads to the Enclave Library. Also, I acquired the Key of the Ancients from pickpocketing it off of Findal when he was unconscious.