Verifying your other bug fixes, I found a few new ones. They're getting more abstruse, which is of course a good sign.
In this one, the Arch-Lich will keep fighting if you're poisoned and knock it to 0 HP, even if you kill it good and dead. In the screenshot below, it had 15 HP the previous round. So the volley would put it at -28 and I think the 10HP boost wouldn't get it back to zero.
This would make for an interesting puzzle to make the Arch-Lich harder to kill so you may want that. But I didn't see anything in the codex to indicate that. I suppose this could be resolved either by noting this in the codex, checking for the total net hit points, or cutting combat off and saying the arch-lich is dead if you hit 0 HP, before the check for poison regeneration.
