Imp Protector Nagafen's Lair
 

Enchanter friend charmed an Imp Protector and once we made it to the Efreeti Room it fell through the floor and killed our group of Taqu, Chantule, and I on my cleric, Billius. We tried to run back and he was back above ground but once a spell was cast on him, pacify I believe, he went right back into the floor and killed us again under the world.