On the very final step of Hell Hath No Vacancy you are to close a hellrift. After waiting for the Living Siege to come out, if you kill it too quickly then you can’t close the rift. You get a “You cannot do that” message instead. You have to let the Living Siege take a step or two, otherwise the game doesn’t register his death and you can’t close the rift and have to move to a different one and try again.
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