The last spoilers of the game, reveal that Odin is actually a spirit of a past king, that has possessed the body of a woman named Alina.
Long ago, in the time of the Crimson Dragon, a tribe gave the name Odin to their strongest King as a homage to the Norse gods. They built Ragnarok and Yggdrasil as they constructed the Transcenders as a perfect army.
Odin later tried to defeat and gain the power of the Crimson Dragon and Earthbound Immortals, but failed and had his soul sealed in Yggdrasil.
Much later, a team of scientists arrived on the island and began exploring Yggdrasil with over half the team falling sick and dying of unknown causes. At the top they discover Surtr and unlock his casket, releasing one of the bindings on Odin's Soul.
Odin uses that to direct Alina, the daughter of the Scientist writing the journals, into unlocking the full seal, but the Scientist takes the brunt of the mist and houses Odin's soul who attempts to force him into beginning his plans for conquest, and in the end, the Scientist chooses to commit suicide and take Odin with him.
The plan didn't work, and Odin possesses Alina in his place.
The player later duels Odin on Yggdrasil 4f and defeats him. After defeating Surtr, Odin teleports the player and his friends from Yggdrasil to Bifrost. While continuing to Duel against the endless amount of Transcenders, Odin reveals to the hero that Bifrost has the power to corrupt and control Duelists who have darkness in their hearts.
Odin in an unmasked version, is the final boss of the game. After his final defeat, Odin attempted to take every one on the island with him but failed and was killed by the very building he caused to collapse.
In the first duel against him, Odin plays a WATER deck named Song of Providence, with more Sea Serpent monster cards.
In the third and last duel, Odin, as the final boss, plays a powerful Dragon deck named Ragnarok Soul, based on the quick summon of powerful Dragon monsters, like Gungnir, Dragon of the Ice Barrier (named after Odin's Spear), Red Eyes Darkness Metal Dragon, Black Rose Dragon, King Dragun and especially the powerful F.G.D.