Biography
Early life
Adopted by Odin and Frigga at the end of the Asgardians' war with the Jotuns, Loki is treated as a prince of Asgard and was never informed of his true heritage throughout his youth. Loki is smaller and thinner, and has a darker hair colour while paler in complexion than the Asgardians. Throughout their childhood Loki spent much of his time trying to prove himself as Thor's equal, while studying magical arts rather than physical prowess.
Thor
"That was just a bit of fun, really."
―Loki[src]
Admittedly jealous of his step-brother, Thor, and anxious about a kingdom ruled by the loud and violent God of Thunder, Loki allows several Jotuns to enter Asgard, who then proceed to try and steal the Casket of Ancient Winters during Thor's coronation. Later Loki admits that it was 'just a bit of fun' meant to ruin his brother's special day and to keep Asgard from his reign for a short while longer. In the wake of this intrusion, Thor is eager to launch a counterattack, and Loki appears to attempt to dissuade him while possibly actually goading him into action. On leaving, Loki leaves word with a guard to inform Odin of their departure, although whether this is through concern for their safety or desire to make Thor lose favor with Odin is unclear.
Once in Jotunheim, Thor leads himself and his friends into conflict and attacks the Jotuns even after being granted safe passage home. During the ensuing fight, Loki uses his abilities to save his brother and friends in several instances, including creating false versions of himself and hurling magic daggers at the Jotuns. He is then attacked by another that siezes him by the wrist. Loki is surprised by his own resistance to the Jotuns' freezing touch and sees his flesh turn Jotun blue and then return to Asgardian colour, a revelation that sews doubt about his origins in his mind. Odin arrives and takes the group back after Laufey promises that Thor will have the war and death he desired. Thor and Odin exchange heated words and insults until Odin, saddened by his son's arrogance and lack of wisdom, decides to punish him. Loki tries to intercede on his brother's behalf but is given a stern reprimand by Odin, prompting him to withdraw and be silent. Odin banishes Thor to Midgard (Earth) while Loki watches in horror; Odin also sends Mjölnir, enchanting it to only allow a worthy person to lift it and acquire the 'Power of Thor'.
Loki and the other warriors go to the healing room to treat their wounds. Loki still wonders about the changing of his flesh on Jotunheim and decides to see if he can induce it using the Casket of Ancient Winters. While he lifts it, visually repeating to himself that 'this cannot be, this is impossible', his skin up to his hairline turns Jotun blue and his eyes turn Jotun red. He is interrupted by Odin and confronts him regarding the incident. He learns that Odin discovered him as an infant left to die in the temple of the Jotuns during the final battle of the ancient war. On Loki's heated insistence, Odin also reveals that his purpose in rescuing him was not solely out of compassion, but also in the hopes that peace could be brought permanently through Loki, although he states that those plans no longer matter. Infuriated that he had been lied to and had been taunted with the promise of a possible birthright, Loki shouts hatefully at Odin and, overwhelmed by the stress of his family falling apart coupled with the impending war with Jotunheim, Odin falls into the deep "Odinsleep" in front of him. With Thor already banished to Earth for the attack on Jotunheim, Loki is offered the position of king by his mother and assumes the role of Asgard's regent. From his position of power he goes briefly to Midgard to lie to Thor telling him their father has died and that their mother forbids his return, as well as trying unsuccessfully to take Mjölnir for himself. He then visits Jotunheim under the guise of trying to repair the damage his brother has done, but instead offers Laufey a chance to slay Odin while he sleeps, promising to return the Casket to him in return, which Laufey accepts.
When Sif and The Warriors Three disobey Loki's command to wait for his word by going to Midgard to retrieve Thor, he confronts and freezes Heimdall for allowing them to leave. He then sends The Destroyer after them to eliminate everything in its path and ensure that Thor cannot return home. This action proves his undoing when Thor's courage in confronting the automaton paves the way for his return, and just as Loki betrays and kills Laufey in Odin's chamber, Thor arrives to challenge him over his actions. The resulting fight quickly moves to Heimdall's Observatory where Loki has connected the Bifrost to Jotunheim, threatening to destroy it. Thor's power ultimately overpowers Loki's cunning, at the cost of the observatory and the Bifrost.
As Loki falls into the abyss below, the spear in his hand was grabbed by Thor who in turn was anchored to the remnants of the bridge by the newly-awakened Odin. He appeals to his stepfather that by annihilating the Jotuns he was doing what was best for Asgard. Odin sadly rejects this, and with his Asgardian life now in tatters, Loki releases the spear and allows the wormhole created by the Bifrost's energy to claim him.
The trickster is not so easily felled however, and sometime later an apparition of himself appears on Earth, where he begins to influence Erik Selvig, who has been summoned by S.H.I.E.L.D. to turn his scientific knowledge to the task of unlocking the secrets of a mysterious blue-glowing cube, which would supposedly be the key to unlimited sustainable energy for Earth. Loki's apparition whispers words of encouragement to proceed.