After the 3rd Tier fight, "A History of Violent Beatings", Baeloth summons Najim, the genie, into the arena for discussion. A persistent cloudkill (from the wand) is left over from the fight and both Baeloth and Najim teleport right into it. The Cloudkill causes Najim to turn red circle hostile (despite taking no damage...considered an attack) for rest of game and it is not possible to talk with him at the end to portal out as he is hostile and dialog cannot be initiated. Game cannot be finished.
Najim should not turn hostile against the party ever. He is virtually invulnerable anyway afaik. This will allow players to speak with him at the end to teleport out of the Black Pits.