Surtr was the host of the tournament, the Duel of Legends Cup. He invited the greatest duelists in the world to come to his island Ragnarok, and participate in order to become the king of Duel Monsters. He didn't tell his guests anything about himself and was quite mysterious about the purpose of the tournament.
At the end of the tournament, he was defeated in the final Duel, by the player. Surtr was then about to explain how he was able to recreate the Earthbound Immortals. Before he did, Odin arrived and sent everyone to Bifrost, an underground tunnel in Yggdrasil. When everyone in the tournament and Surtr are there, Odin told Surtr that he is also a Transcender robot, who works for him. Surtr denied this, so Odin took him by force further down Yggdrasil to examine him as to how he can deny the fact of being a Trascender.
Surtr later returns to help the player by damaging Odin. He claims to be free from Odin's control. But Odin survived the hit, revealing his true self, and then destroys Surtr.
A letter, written by Alina's father, reveals that Surtr's body was inside a tomb, meaning that this is, if only, the oldest Transcender ever created.
Surtr plays a Gemini-themed Deck entitled Fire Knight.