The Duel at the Bifrost Bridge was an attempt by Thor to prevent his adoptive brother Loki from using the Bifrost Bridge to destroy Jotunheim.
Background
Loki learned that he was the son of the Frost Giant king Laufey, who abandoned him as a child to be found and raised by Odin, the king of the Asgardians. Since Thor was the "favorite son" of Asgard and destined to be its king, Loki felt rejected by both of his fathers. Loki invited Laufey to Asgard so he could kill Odin, who was incapacitated in his "Odinsleep", but Loki killed the Jotun King, doing something neither Odin or Thor would do.
Thor, in the Battle of Puente Antiguo, proved worthy of Mjølnir and to return to Asgard after his exile. He learned from Sif that Loki lied to him about their father's death.[4]
Duel
Loki activated the Bifrost to begin the destruction of Jotunheim by unleashing its full power. He explained that he only wanted to be Thor's equal in Odin's eyes, but now he desired the throne because he will have accomplished what no one else has done in destroying the Frost Giants. The two began to fight. As Loki fell onto the Rainbow Bridge, Thor placed Mjølnir on his chest, making him unable to move.
Loki taunted Thor that what he has set into motion was unstoppable. Meanwhile, Odin awoke from the Odinsleep.
Thor realized that Loki spoke the truth and began to hammer the Rainbow Bridge with Mjølnir. Loki told Thor that if the Rainbow Bridge was destroyed, Thor would never see Jane Foster again. Thor continued to pound the bridge until it collapsed. Both fell over the side, only to be caught by Odin.
Loki falls to his apparent death
Loki told his adopted father that he did everything to impress him. Odin listened, but disappointment showed on his face. Loki decided to release his grip and fell into Yggdrasil itself.[4]
Aftermath
Loki was found by Thanos, who showed him the potential power of the Tesseract and gained Loki's servitude.[5]
When Thor sought to go to Earth because Loki was in Stuttgart causing a hostage situation,[5] Odin used dark energy to transport him.[6]
With the Bridge destroyed, Marauders took advantage of the Asgardians' lack of transportation and plundered Vanaheim and other worlds.[7]
