Help! I can't do any damage to Hedrack. All my hits score exactly zero point of damage to the guy. He already called Iuz and Cuthbert already told him what to go do with himself. I have defeated every vbugbear, zombie, etc. in the room! All but Hedrack, and he doesn't do anything on his turn except laugh. I feel like I am wasting time, like it's a bug or something. Anyone know why this is happening? Thanks!

edit: never mind. I went down the hall until I was out of combat mode, then back and struck him again. He died very quickly. :)

Good that worked out for you.
I think hedrack had stoneskin or some other damage reduction spell on him.

I'm not aware of any DR sufficient to consistently reduce your damage to zero. Stoneskin is only DR 10. Something should be getting through that.

Hedrack is an exceedingly fragile foe (relative to when he appears in the game), so it does make sense that there might be some scripts in there to help him stay alive that misfired.