Because you also fight the Beast Clergyman during the Maliketh fight, and given that you can choose to kill him earlier in the game, it is most commonly thought that there's some sort of time travel going on. The idea is that Gurranq is most likely a past or future version of Maliketh, as it would seem natural that the only character to wield death as a weapon would also have the ability to negate its effects. This Reddit thread provides some interesting discussion on the topic.