The devils are within earshot, from the screams of the frying clerics; while his spells don't kill them, it leaves them badly wounded, each using a quick healing spell on itself, before drawing their weapons and barreling down the hallway, roaring, and drawing the attention of the erinyes, who will take a couple rounds to arrive. Meanwhile, the party spread out, filling the hallway, standing before Draiss, to protect him from the charge.