UPDATE:
The Thursday night group went in again - 2 barbarians, 1 sorcerer/warlock, and a light cleric.
Only the light cleric made it out alive.
Once more, they struck too deeply into enemy territory in pursuit of fleeing kobolds, ending up in the audience chamber of their chieftain, Meepa, Bastard of Venthavaxus (a half-red dragon kobold). She burned down the raging barbarians with her fire breath as kobolds swarmed in from all five doors in her throne room. The sorcerer/warlock dug in to try to save the dying barbarians as the light cleric led the tactical retreat to the rear. It was all for naught as the sorcerer/warlock was also overrun and slain.
They try again next Thursday.