If the creature is able to defeat Marr by destroying his portal, the necromancer is banished from the world of the living and the creature reverts into their previous human self, returning to his position as commander of the Galleykeep. If the creature fails, Marr takes the vapour by force and it is implied that Marr uses it to conquer the world of Titan with the creature either as Marr's second-in-command or slaughtered by his crew.
If the creature defeats Marr by destroying his portal, they are banished from the world of the living and return to their human form, regaining their position as commander of the Galleykeep. If the creature fails, Marr takes the creature's vapor by force, suggesting he will use it to conquer Titan with the creature either becoming Marr's second-in-command or being killed.