He is split at zone in/out.
2 of his place holders are above the ledge (you need to go through the entire zone and get to the end to find them). If your hunting him at zone in, find a tracker/someone to verify he isn't spawned above the ledge.
The ramped tunnel just above his first zin placeholder is a safe spot (below the standing guards where you fall through floor). Nothing wonders there. Below that point all the way down are all wonderers, so break the spawn there (if all wonderers gone you get 2).