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.
As a reward for retrieving the root, the witches lead the creature to an elf, the original thief of the Vapours, whom the creature can extort for information on how to access the Galleykeep, Marr's flying vessel. Aboard the Galleykeep Marr reveals the creature's identity and demands that he surrender Grog's box, which contains the Vapour of Elven Magic.