I started the portal quest with my 78 necro.
sure enough he pops just inside the cave to the left (west) of the waterfall.
I saw one wanderer so I rooted and dotted him first. For a green mob (to my 78) he seemed to have a lot of HP I thought. This was A Darkfell gnoll, with 34K hp. I haven't killed any of these guys in the past.
I snared and rooted the Prophet Spirit and dotted him till he died. He only came unrooted once and while there is not a lot of space in front of the cave it was easy to move aroud and reroot him.
He had 79.3K hp.
The fight took about 2 minutes for me and I suspect more adds would come if it went on too long, it seemed like I saw mobs go into the cave earlier

Ancient Charm
Giant Blood
Giant Bones
Giant Parts