When he's up, he roams the north western area of the zone. Walks up and down the stairs in that area, approximately +950, +1300. I was killing the wandering mobs around that area to get him to spawn. Seen him in the form of a gnoll both times I killed him.
I got it to pop, pathing up and down the long stairwell going from the 2 PH area of the AN ABRADED GENARI up to almost the center of zone.
Its the first time I have seen this pop, but have been killing this mobs ph repeatedly.
I hope that helps you out. There are 2 pathers on this stairwell. 1 is the bad type, the other is the good type. The bad type is obviously the PH. If its not a totally random mob.
EDIT*** There was another BAD type mob on this stairwell also.