I just went in today with a group of level 16-18 and we killed the roaming corpse no problemo.. After that though, 3 of them spawned and were all atleast a level higher then the roaming corpse.. So on our way back from Fort atla :P we found all 3 in the same spot we left em. They don't seem to wander and you can pull them 1 at a time with a ranged attack.
These things do drop from Roaming Corpses, as we found out on our first visit to the Cursed Tomb last night. Both characters were level 17 and the Roaming Corpse conned Orange. A quick defeat of the Corpse produced the Corpse Crawler which then annihilated us entirely and completely. And for the final boot to the eye, it then hung out by the gravestones and would not wander. Whee...
Wait, do these thing roam singely or do they spawn after you kill the roaming corpses? I was killed by one that appeard out of nowhere after I kill the wandering corpse.
These things are much higher level then posted here, they're purple to a lvl 18 and are much harder to kill then the ghouls and other roaming things in the enterance, my guess is they're 25ish since they're about as tough as the commander