While battling at the Infernal Hordes, after the wave time ended, some foes are untargetable, so I can’t kill them. Even running and surviving a while, they just don’t die because I can’t target them.
I think I’ve had the same thing happen to me twice. They were 4 henchmen with axes that show as a single red spot except when they chase you then there are two red spots. There was no way to kill them and the only solution I could find was to let them kill me, which was painstakingly slow. Then when I revived they were gone.