Bifrost Bridge



The Bifrost Bridge, also known as the "Rainbow Bridge", is a star portal which connects all the Nine Realms together. However it can only be opened by the guard of the bridge, Heimdall and it will only open if permitted to; in fact the bridge calls upon powerful energies from deep within Asgard to function, and could even destroy an entire planet if left opened.

History
Thor, Loki, Sif and the Warriors Three used the Bifrost Bridge to reach Jotunheim and attack the Frost Giants by surprise after being told by Loki they were going to attack Asgard; even though Heimdall was not happy letting them cross the bridge. Later, Loki used the Bifrost Bridge again to Jotunheim to ally himself with Laufey, so that they could attack Asgard through the Bifrost Bridge rather than through one of Loki's secret pathways.

Once again Sif and the Warriors Three used it to reach Earth to rescue Thor and bring him back to Asgard after being banished to Midgard. In order to prove himself worthy of the throne of Asgard, Loki wanted to use the Bifrost Bridge to completely destroy Jotunheim and he was able to open it after freezing Heimdall and killing Laufey.

Upon returning from his exile, Thor chose to destroy the Bifrost Bridge in a duel against Loki, so preventing the annihilation of the Frost Giants.

After the Bifrost Bridge was destroyed it has been regenerated with the energy obtained from the Tesseract, and Heimdall continues to guard the Bridge.

Thor and his friends used the Bifrost Bridge multiple times during war with the Dark Elves.