The Attack on Jotunheim was an attempted attack on Jotunheim led by Thor after some Frost Giants managed to enter Odin's Vault and attempted to steal the Casket of Ancient Winters on Thor's coronation day.
- "I think you’re right. About the Frost Giants, about Laufey, about everything. If they found a way to penetrate Asgard’s defenses once, who’s to say they won’t try again. Next time with an army."
In 900 B.C, the Asgardians battled the Frost Giants on Jotunheim during the Asgard-Jotunheim War, ultimately winning the fight. Odin made a truce with Laufey, leader of the Frost Giants and confiscated the Casket of Ancient Winters. He also took an abandoned baby and adopted him, naming him Loki which was revealed much later.
During Thor's - Odin's biological son - coronation, the truce was seemingly broken when the Frost Giants entered Odin's Vault and tried to steal the Casket of Ancient Winters, but not before the Destroyer interfered and thwarted the theft. Thor, enraged then swore revenge on Jotunheim and gathered Loki, the Warriors Three and Lady Sif to accompany him on the journey to Jotunheim. Thor then asked Heimdall to keep it a secret and then Heimdall transported them all to Jotunheim.
This section needs a rewrite
- "At least make it a challenge for me!"
Once they arrived on Jotunheim, they journeyed through the snow eventually making their way to Laufey. Thor questioned him about how his people were able to get into Asgard. Laufey accused Odin of being a murderer and a thief and told Thor he was just a boy. He then allowed them to go, but a frost giant antagonized Thor by calling him a little princess which enraged Thor.
Thor immediately attacked the frost giant and a fence battle ensued between the Warriors Three, Lady Sif, Loki, Thor, and the Frost Giants as the fight continued Thor clearly was enjoying the battle. At first Thor and the others can hold their own using their skills to defeat the giants, but Thor who is getting more engrossed in the battle calls Laufey to send out more foes, the others start to struggle. Sif is almost thrown off a cliff, Volstagg is burnt by the icy touch of one of frost giants and warns the others to avoid physical contact with the giants. In the middle of the fight one of the giants manages to grab Loki's arm but instead of burning it it causes the skin on his arm to take on the appearance of a Frost giant's before he gets out of the creature's grip and his arm returns to normal.
When Fandral is skewered by an ice spear, Sif orders a retreat which Thor doesn't notice and continues the fight while the others flee. Laufey summons a monster to chase after them which corners them on the edge of the realm since Heimdall won't open the portal because of the risk. Thor quickly arrives to kill the monster only for the group to be surrounded by thousands of giants. When all seems lost Odin appears. Thor wants his father to fight with them but Odin tried to negotiate with Laufey saying this battle was just the act of a few "Children" but Laufey says that Thor's actions just broke the truce and prepares to attack only for Odin to teleport everyone back to Asgard.
- "Through your arrogance and stupidity, you've opened these peaceful realms and innocent lives to the horror and desolation of war!"
Loki later revealed that he had informed a guard of their journey to Jotunheim, who in turn told Odin. During the fight Loki began to suspect about his true heritage when the touch of one of the Frost Giants had no effect on him despite it caused frost bite on the rest. Loki raged to Odin about this fact as he fell into the Odinsleep.