Well, the flail of ages does acid damage. I usually give one of my tanks that to make sure they finish him off. Also, I usually send in a couple fireballs for good measure. Also I think there's a bug with Agawhosiwhatit's Scorcher. It's supposed to do fire damage to anyone in the path, but I fired it through my party once, just for kicks, and only the target took damage. Then again, I think that was BG1, and there were a lot of bugs in that game (like Druids, Clerics, and Bards getting shafted on their usablility, and rangers not getting Dual wield
)
and that's my 2 cents...