The last group of cursed revenants seem to be bugged. You should be able to kill them, if they die far enough away from cursed fire. I used blood rain and bless to get rid of most of the cursed fire and killed the first cursed revenants. But the trio in the back always respawns in that particular corner wherever you kill them. So I just cleansed some of the cursed fire in front of their room, snuck past them and teleported the rest of the group with the pyramids.
