This is one of Nail's players here.. I'm the Psion 14 (Shaper).. that was a challenging encounter to be sure! it took us two tries to do it (4 deaths on the 1st attempt, and 3 deaths on the 2nd).. fortunately, there is (was) plenty of coin to pay for the raise deads, and there's been no level loss penalty because of the existence of Manifest (which the "usual" DM added, though I suspect it may not remain much longer)..
I think my character has been the only one to not lose a life from either session.. though my luck will turn I'm sure.. having Nail as my DM in another group, I'm properly cautious about things.. the other players are not.. it doesn't hurt that I've got a very high CON and Dim Door + Teleport capability either!
Kerzit was a serious challenge to be sure! That CON damage took out at least one character.. in fact brought me down from 161 HP to 36 on one attack (9 CON damage)..
I'm not really the best person to recap things, I don't really remember things in a way conducive to that.. but Dim Dooring in with a couple of Astral Constructs was of great use to hold off the summoned demons.. (they lasted longer than I thought they would).. I also tried quite a few overchanneled (PP 15) Crystalstorms (from Dragon #317).. I do note from earlier in the thread that Kerzit would have failed that DC 26 fort save on either a 1 *OR* a 2.. 10% chance!!!! never was able to manage it though.. I was really hoping on giving him some of that CON-damage goodness back at him, but no such luck!
BTW, Nail, if you feel that the CR (and thus the earned XP) should be upped from 20 (seeing as we have NO cleric available), feel free! :)
I'm looking forward to the next bit.. didn't make 15th level, but that XP did help! It was a great time.. :)