Ghasts and Wights
I'm curious, but would ghasts and wights work together to haunt and invade adventurers who have set camp in the wilderness? The ghasts and wights wouldn't be swayed by an evil cleric or necromancer, but there is someone in the group who unknowingly seems to have undead gravitate towards his proximity. It's more like the person acts as a beacon to undead.
So, yeah, there are wights and ghasts in the area, so I'm curious if they would group together as they advance upon the camp.