Can't find Brithvar, and Nere isn't dying from poison.

Lets just say, I suck at combat. I tried fighting Nere 3 times now and each time my team goes straight to hell. I decided to look at online advice and some said to ally with Brithvar and his buddies. Problem is, I can't find him anywhere in the area. So, I eventually decide to take 3 long rests in a row to easily kill Nere. However, he's not dying. Three days in the gas room and he struts out no problem. Am I missing something here or am I just stupid?