Hello!
I dont think that the undead levels are calculated correctly with palemaster and wizard levels.
The characther in question levels are 6 wizard, and a level 5 palemaster And seem to be summoning a tyrantfog zombie, instead of a skeletal chieftan.
While summon undead grants them a wraith.
..And the spell "Animate dead" does give him a skeletal chieftan. Not sure if its intentional, but I figured it was worth bringing up.