When Surtur destroyed the Burning Galaxy on his crusade to destroy Asgard, a race of beings called the Korbinites left their planet in a massive fleet. Before the journey, however, their scientists created a guardian who would travel with the fleet and protect them during their journey. Their first guardian, Alpha Ray, was riddled with problems. He was a mindless automaton, and deemed too unstable in both body and mind to be their protector. His body was put into stasis in a Meta-Orb and the Korbinite Bill was selected after various tests and challenges and was turned into a cyborg.
When the Korbinite fleet neared the Milky Way Galaxy, it was detected by a SHIELD satellite and Nick Fury asked Thor to investigate. When Thor arrived in the vicinity of the fleet, Bill's sentient ship, Skuttlebutt, detected him as a threat and opened fire. Thor boarded Skuttlebutt and he and Bill fought. During the fight, Thor lost his grip on Mjolnir for more than 60 seconds and was transformed into Donald Blake. Curious, Bill picked up the hammer and was deemed worthy, instantly giving him the powers of Thor and a costume of similar design.
Sensing this, Odin transported both Thor and Bill to Asgard, where Bill demanded he be allowed to keep the hammer because he had beaten Thor. However, Odin said that the contest was not fair because Thor had an artificial limitation, so he temporarily restored both of their powers and arranged for them to fight to the death in the realm of Skartheim, a lava-filled wasteland. After a long and grueling battle, both combatants succumbed to exhaustion and collapsed. However, Bill's race was naturally enhanced by warm climates and he awoke before Thor but refused to take his life, thus passing Odin's final test.
Odin then created a new hammer, Stormbreaker, imbuing it with all the powers of Mjolnir, but none of the limitations. Thor and Bill became friends and they, along with Sif, returned to save his people from the armies of Surtur.
Though Thor was called back to Asgard before the Korbinites were safe from Surtur's minions, Sif stayed with Bill to continue fighting the demons and because she was curious about him. It was during this time that she learned from Skuttlebutt the extremely painful and difficult trials Bill had to undergo to become the guardian of his people and that he was the only survivor from many volunteers. When Surtur finally arrived at Asgard, Sif and Bill were called back by Odin, and they were placed in charge of leading the Asgardian army on Earth while Thor and Odin fought against Surtur's army in Asgard.
During the battle, Odin hurled Surtur and himself into a fissure in the ground, seemingly killing them both. Thor, unable to accept his father's death, refused to lead the Asgardians and asked Sif to lead them in his stead as he began a journey to find Odin's spirit. Sif asked Bill to stay in Asgard and help her lead the Asgardians during their recovery from the war with Surtur. During this time, Bill and Sif became very close, and a romantic relationship was hinted at but never realized before Bill eventually left to return to his people.
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