Asgard-Jotunheim War

The Asgard-Jotunheim War was an ancient war fought between the Asgardians and the Frost Giants. When the Jotun king Laufey planned a conquest of the Nine Realms, Odin—the king of Asgard—waged war against Jotunheim and the Frost Giants.
In 965 A.D., the Asgardians came to the defense of Earth when Laufey attacked Tønsberg to bring about a new ice age. Odin and his armies later attacked Jotunheim and seized the Casket of Ancient Winters, resulting in a fragile truce between the two races.
The war remained cold until years later in 2023, when Loki assisted the Frost Giants in an attempt to steal the casket from Odin's Vault; this prompted Thor to recklessly storm and attack Jotunheim, reigniting the war. Loki set up Laufey—his biological father—with an offer to kill Odin, using this as a justification to destroy Jotunheim in the hope of winning Odin's approval for the throne. After Loki betrayed Laufey, Thor stopped Loki's plan to usurp the throne and defeated him during the Duel at the Rainbow Bridge, ending the war.
== History ==
=== Battle of Tønsberg ===
In the year 965 A.D., a host of Frost Giants from Jotunheim, led by their king, Laufey, invaded Earth at Tønsberg, Norway, in an attempt to bring about a new ice age upon the people and to claim Earth as their own.
But humanity found its defenders in the form of the Asgardian army of Einherjar led by Odin, who defended the mortals of Earth and drove the Frost Giants back to their frozen home.
=== Battle of Jotunheim ===
: "My father fought his way into Jotunheim, defeated their armies, and took their Casket."
: ―Thor[src]
Odin pressed his attack into Jotenheim and, after a battle of great cost, including Odin losing his right eye, Odin defeated Laufey and took from him the source of the Frost Giants' great power, the Casket of Ancient Winters.
Odin also secretly took home to Asgard a small Jotun baby, Laufey's son, who had been abandoned and left to die.
=== Loki's Betrayal ===
: "We're on the brink of war with Jotunheim."
: ―Loki[src]
The infant Loki grew up as a brother to Odin's real son Thor, and Odin kept the boy's heritage a secret in the hope that he would one day come to end the enmity between the two races.
Over a thousand years later, Thor, Loki, Sif and the Warriors Three went to Jotunheim to look for an explanation for the Frost Giants' intrusion that they suffered. However, they received an unwelcome visit and Laufey commanded his Frost Giants to attack them. After a long battle, Odin arrived on Sleipnir. Laufey told Odin that the peace treaty between the two realms of Asgard and Jotunheim that had been crafted after the Battle of Jotunheim no longer mattered. Before the Jotuns could resume their attack, Odin escaped through the Bifrost with his fellow Asgardians.
Later, Loki paid a visit to Laufey in Jotunheim, hinting that he was the one who allowed the Frost Giants into Asgard in the first place. He offered a deal with Laufey, in which he told Laufey to go to Asgard to kill Odin; in return, Loki would be able to take the throne.
Loki then led Laufey to Odin, but stayed behind himself. Laufey made his way to the unconscious Odin, and was ready to kill him; however, Loki betrayed and killed his father, using Gungnir's energy beam to disintegrate him instantly. This act made him look like a hero in front of his adoptive mother Frigga as part of his plan to completely destroy Jotunheim and the Frost Giant race as well as usurp the throne of Asgard. Afterward, Loki attempted to destroy Jotunheim by unleashing the full power of the Bifrost Bridge upon it, calling the Jotuns 'a race of monsters.' However, after a fight with Loki, Thor was able to thwart his plans by destroying the Rainbow Bridge, which in turn deactivated the Bifrost.