The Bifrost Bridge was an interstellar portal which allows instantaneous travel to any of the Nine Realms and planets beyond. The Bifrost Bridge is guarded and controlled by Heimdall and/or the King of Asgard. The Bridge can only be activated by either the sword of Heimdall or the spear Gungnir wielded by the King of Asgard. Once opened from within Heimdall's Observatory, the bridge calls upon powerful energies from deep within Asgard to function, and could even destroy an entire planet if left opened.
- "If your return threatens the safety of Asgard, Bifrost will remain closed to you. And you'll be left to die in the cold waste of Jotunheim."
"Couldn't you just leave the bridge open for us?"
"To leave the bridge open would unleash the full power of the Bifrost and destroy Jotunheim, and with you upon it."
- ―Heimdall and Volstagg
Thor, Loki, Sif and the Warriors Three decided to use the Bifrost Bridge to reach Jotunheim and attack the Frost Giants by surprise following an unexpected breach of Odin's Vault. Loki prepared to decieve Heimdall, however the Bridge's guardian, knowing their intent and curious as to how the Jotuns had slipped by him, allowed them into the Observatory. After activating the Bridge, Heimdall informed them that if their return threatened Asgard, he would keep the Bifrost closed to them, and informed Volstagg that the Bridge would eventually destroy Jotunheim if left open whent he rotund warrior suggested that he leave it open for them.
As they fled from the Frost Giants, Loki, Sif and the Warriors Three returned to the Bifrost site, asking Heimdall to open the Bridge to allow their way, however there was no response. Only when they and Thor were completely surrounded did the Brifrost open, allowing Odin, riding Sleipnir, to arrive. After Laufey refused the All-Father's request to excuse his son's and friends' incursion, Odin signaled for the bridge's activation, and the Asgardians were pulled back to their home realm.
Banished to New Mexico
Upon their return to Asgard, Heimdall was dismissed from his post by Odin as he and Thor argued. Odin proceeded to use Gungnir to activate the Bifrost, before stripping Thor of Mjølnir and his armor before banishing him to Earth, to be hit by Jane Foster and her colleagues.
Later, In order to prove himself worthy of the throne of Asgard and distance himself from his Frost Giant herritage, Loki decided to use the Bifrost Bridge to completely destroy Jotunheim. Loki used the Bifrost Bridge to travel to Jotunheim so that he could forge a false alliance himself with Laufey, offering him access to Asgard through the Bifrost Bridge rather than one of Loki's secret pathways.
Heimdall was suspicious of Loki's disguised actions while away, having been unable to see him with his omni-sense, and in response Loki ordered him to keep the Bifrost closed until he had dealt with the issues caused by Thor.
Knowing that Loki was acting out of his own selfish interests, Heimdall's omni-sense allowed him to learn that Sif and the Warriors Three wanted to use the Bifrost to reach Earth to rescue Thor and bring him back to Asgard after being banished to Midgard. Skirting Loki's order to not allow any through the Bifrost, Heimdall instead left Hofund behind for them to use.
Used as a Weapon
Having seen the Bifrost being activated, Loki decided to send the Destroyer to Earth to eliminate Thor and his allies to ensure his rule. After confronting Heimdall, Loki declared that he was relieved of duty and then froze him using the Casket of Ancient Winters. Using Gungnir, Loki activated the Bifrost to send the Destroyer to Earth, and after it was defeated, he then opened the Bifrost to Jotunheim, welcoming Laufey and a few of his men to Asgard. 
Once Heimdall was able to break free of the ice, he opened the Bifrost to allow Thor and the others to return. After Thor confronted him in Odin's bedchamber, Loki returned to the Observatory to activate the Bridge, intending to use Laufey's infiltration of Asgard as justification for the Frost Giants' destruction. Once the Bifrost was opened to Jotunheim, Loki used the Casket to freeze the Bifrost, so that its power would continue to build until Jotunheim was destroyed.
As Loki and Thor dueled on the rainbow bridge, the Bifrost continued to launch its full power at Jotunheim, the effects of which began to be visible on other worlds in the Nine Realms. Unable to get close enough the Observatory in order to shut it down, Thor realized he had to destroy the Bifrost Bridge, bringing Mjølnir down with full force on the rainbow bridge. After it exploded, the Bifrost fell apart, preventing the annihilation of the Frost Giants, and created a temporary wormhole which Loki allowed himself to fall through after Odin condemned Loki's actions.
Out of Action
Because of the Bifrost's destruction, Odin was forced to use dark energy to transport Thor to Earth, at the cost of both their health, in order to retrieve Loki, who was attempting to use the Tesseract to conquer Earth.
Reestablishing Contact with the Nine Realms
Once Thor returned with Loki and the Tesseract, the Asgardians were able to regenerate the Bifrost Bridge using the energy obtained from the cube, and Heimdall continued to guard the Bridge.
Thor and his friends used the Bifrost Bridge multiple times to pacify the Nine Realms, the last campaign of which sent them and several Einherjar to Vanaheim. Thor arrived after the battle had already begun, launching Mjølnir at a Marauder while the Bridge was still open. 
Once the Marauders were defeated, Volstagg, Fandral and the Einherjar began transporting their prisoners back to Asgard through the Bifrost for imprisonment, transporting dozens at a time. In order to infiltrate Asgard, the Dark Elf Algrim disguised himself as a Marauder so that he was transported amongst their prisoners.
Temporary Shut DownDark Elves' first attempt assault in their War against the Asgardians, Odin ordered the Bifrost shut down to prevent anyone from leaving, forcing Thor to ally with Loki in order to find another way off Asgard.
Thor used the Bifrost Bridge to reunite with Jane Foster days after the resolution of the Dark Elf Conflict and the death of Malekith.
Loki's Disguised Reign
Return from Muspelheim
With Heimdall banished from Asgard, Loki employed Skurge to take his place as Guardian of the Bifrost. While Skurge was operating Heimdall's Observatory, Thor called on Heimdall to help teleport him safely back to Asgard, though Skurge was at the time was attempting to impress to Asgardian women in the Observatory. Eventually one of the women pointed out the request to use the Bifrost, however, Skurge was unaware that Thor was concurrently being chased by a Fire Beast on Muspelheim. Upon activating the Bifrost, Skurge returned Thor to Heimdall's Observatory, but also inadvertently the head of the Beast who happened to be in the Bifrost's scope of teleportation.
Thor and Loki used the Bifrost to teleport to Earth in order to find their father. However, upon Odin's later untimely demise in Norway, Hela was released from her imprisonment. After witnessing her destroy Mjølnir effortlessly, Loki called for safe passage through the Bifrost back to Asgard at once. When the Bifrost's beam reached Earth, Hela just managed to step into the light and enter the Bifrost, which ensued a skirmish between her, Loki, and Thor. She manifested blades while inside the Bifrost, quickly thrusting Loki out of the light and into the void, and soon did the same to Thor, inadvertantly causing the pair to emerge on Sakaar, albeit at different times. 
Hela arrived on Asgard and immediately slew Volstagg and Fandral, who were guarding the Bifrost with Skurge, before moving to take control of Asgard. As she did so, Heimdall infiltrated the Observatory and stole Hofund in order to prevent the Bifrost from being used to assist Hela's plans to conquer the Nine Realms and the worlds beyond.
Attempt to Evacuate
As Hela decided she needed to slay innocent civilians in order to find Hofund, one of the Asgardians spoke up before Skurge could begin executing people on her behalf. As Hela and Skurge approached Heimdall's hideout, Thor returned to Asgard, drawing Hela's attention back to the Asgardian Palace and affording Heimdall the oportunity to begin evacuating the Asgardian population.
Unfortunately, the Observatory was blocked off by several of Hela's undead minions and the Fenris wolf, while more of the Berserkers and Skurge cut the off way they had come. As the citizens of Asgard watched, the Berserkers and Fenris were attacked by the Hulk and the Commodore-piloted Valkyrie, and soon Loki and the Sakaaran Rebels arrived to assist. As the Asgardians borded the ship they had arrived on, Hulk and Fenris' battle took them over the bridge's edge, and soon Thor arrived to help Valkyrie fight off more of the Berserkers.
Once Hela arrived, she continued her battle with Thor and Valkyrie, destroying a section of the bridge. Realizing that they could not defeat her since Hela's power only grew the longer she remained on Asgard, Thor realized that they had to allow Ragnarok to occur in order to defeat her. Once Loki threw Surtur's crown into the Eternal Flame, the fire demon was restored and granted his full power. As Surtur thurst his blade into Asgard, destroying it, the Bifrost Bridge was destroyed along with it.
The Bifrost Bridge is a transit system used by Asgardians to travel to the various realms among the Nine Realms and numerous other planets. The Bifrost uses a powerful, rainbow-like energy drawn from the center of Asgard to create Wormhole-like portals that can instantaneously transport people and objects between realms, over millions of light-years of distance. On other realms, the Bifrost appears as a brilliant beam of white light that shines down on its surface, often leaving behind a rune-like pattern burned into the ground.
The Bifrost Bridge is composed of two physical structures in Asgard: Heimdall's Observatory and the Rainbow Bridge, which act as two components of a large machine that channels energy from Asgard to create the portals that allow for transportation. The Rainbow Bridge draws energy from the center of Asgard to Heimdall's Observatory where it is directed to its destination allowing transportation that is precise and accurate. The Bifrost also behaves like a tractor beam, drawing people and objects bathed in its light back to Heimdall's Observatory, such as people wishing to reach Asgard or pulling the Aether from Svartalfheim to prevent Malekith from using it. The beam of energy projected by the Bifrost is powerful enough to destroy a realm/planet if it is allowed to remain open long enough, as Loki tried to do to Jotunheim.
|Appearances for Bifrost Bridge|
In chronological order:
- Not to be confused with the Rainbow Bridge, the Bifrost is the portal generated from Heimdall's Observatory that allows for transport between the Nine Realms.
- However, Thor once described the Bifrost as a rainbow bridge, due to the prismatic energy of the Bifrost resembling a rainbow.
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Thor
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Thor: The Dark World Prelude
- ↑ Thor: The Dark World Prelude, Volume 1
- ↑ The Avengers
- ↑ Agents of S.H.I.E.L.D.: 1.15: Yes Men
- ↑ Agents of S.H.I.E.L.D.: 2.12: Who You Really Are
- ↑ Avengers: Age of Ultron
- ↑ 8.0 8.1 8.2 8.3 8.4 8.5 Thor: Ragnarok
- ↑ The Art of Thor