I just had the strangest random encounter with a groaning spirit. Some 2 or 3 rounds into the battle something happened that gave it temporary hitpoints: 520+ MILLIONS OF THEM as shown on mouse-over and in the rolls box. Needless to say, that battle didn't go very well. I take it that is not a usual ability of those buggers?
I had the exact same thing happen. I had just completed a few quests in Verbobonc and was threatened with retaliation by a man in jail. I got this encounter after leaving for Hommlet and thought it was intentional. I tried everything to kill them and got nowhere. Something I did triggered a new stack of temporary HP to start building. After reloading they didn't reappear.
