During the Virgin Gynocides quest, I explored all the way to the bottom right side of the map and fought 2 or 3 cultists along with a chthonic horror, but I can't kill the horror. All my attacks deal no damage, along with any items I have in my inventory. Is this a bug or is there a trick to this?
Edit: Just checked the wiki; I don't have any anti-demon items that can harm the chthonic horror