OOC: it occurs to me that if PfE works as advertised, then Tarag can solo the adventure now. With a PfE up, he moves as fast as possible to the safe room door, knocks for Thyrin, slips inside, puts a PfE on him, and then they can both safely emerge and Thyrin can disable the summoning devices, and make his way outside.
On the other hand, there's obviously something screwy about the summoning devices, since the elementals appear over 20 minutes and not in 6 seconds, and stick around much longer than 1 round/level. Perhaps they're actually calling devices. Does PfE have any effect on called as opposed to summoned creatures? Won't it be fun for Tarag to find out?