The Battle of Jotunheim was the last great battle in the devastating Asgard-Jotunheim War that occurred on the Frost Giant's home world of Jotunheim. At the great cost of life for both the Asgardians and Frost Giants, the forces of Asgard finally proved victorious over the Frost Giants. Odin personally defeated King Laufey in battle let the King live as an act of mercy. Before departing Jotunheim for Asgard, Odin made certain that the source of the Frost Giants power, the Casket of Ancient Winters was removed from their possession which left their world in ruin for centuries and the Frost Giants hungry for revenge against Odin and Asgard.
The king of the Frost Giants, Laufey, violated a sacred peace agreement enacted many centuries ago by Odin, leading his people on a grand conquest of the Nine Realms. The first target was Earth, where the Frost Giants invaded Tønsberg, Norway. Using the Casket of Ancient Winters, Laufey murdered hundreds of human villagers, until the Asgardians assembled an army of their best warriors and drove the Frost Giants from Earth.
The Frost Giants returned to Jotunheim, supposedly to replenish their forces, but Odin led a huge force of Asgardian warriors against them. After a long, difficult battle, where Odin personally defeated Laufey while suffering the loss of his right eye, the Asgardians defeated the Jotuns. Odin then granted the Frost Giants mercy and offered a truce between the races, a truce that Laufey was forced to agree to. In the process, Odin confiscated the Casket of Ancient Winters.
In the aftermath of the battle, Odin discovered a baby Jotun who had been abandoned in the conflict by his own father, Laufey. He adopted the baby, and named him Loki. With the truce in place, peace between Asgard and Jotunheim lasted for over a thousand years. On the day of Thor's ascension to the throne of Asgard, Loki used his powers to sneak several Frost Giants into Odin's Vault to retrieve the Casket of Ancient Winters but were killed by the Destroyer.