After Marius witnessed the horrors of [[Tristam]] and followed the [[Dark Wanderer]], he then becomes the Wanderer's companion. His Marius' sanity is questionable, as well as his courage, as he . He is tricked by into removing [[Baal]] into removing his 's [[soulstone]] and then is unable to go through the infernal gate in [[Kurast]] to go to [[Hell]] to destroy Baal's the soulstone at the [[Hellforge]].

Some time later, Baal visits Marius, in human form in his cell in a mental asylum. He Marius then narrates the events of [[Diablo II]] to Baal, who he mistakes for [[Tyrael]]. In the end, he Marius confesses to Tyrael that he did not destroy the soulstone and gives it unwittingly to Baal for destroying it to be destroyed at the Hellforge. Baal then reveals himself and kills Marius, destroying the asylum in the process.