So in trying for the oblivion walker achievement I went to the Sacellum of Boethiah to kill all the cultists. However 2 of them are invincible, no hits register but they can kill me. I can't get a follower past them to sacrifice and can't kill them, even dragons/trolls other mobs i've brought near can't kill them. This is a major bug that is not going to let me complete an achievement. Please fix it!