Ragnarök

"To wage war on those who would kill any who cannot defend themselves... To hold back the ever-growing tide of Ragnarök that comes to calm us all. This is not our duty. It is the reason for our very existence."

- Thor

Ragnarök is a doomsday event in Asgardian culture that prophesized the destruction of Asgard and the end of the Asgardian Empire. It was predicted that Surtur, ruler of Muspelheim, would be the one to cause the calamity, and in 2017, it came to fruition with the release of the former heir apparent of Asgard, Hela. Thor deliberately had Surtur unleashed, to cause Ragnarök as a means of killing Hela. While Asgard was destroyed in the event, its people managed to survive and were left as wandering nomads.

A Fateful Prophecy
"The universe moves forever towards Ragnarök. This is its nature."

- Odin For countless millennia, Asgardian culture has foretold of an event that would bring about the destruction of their homeworld. Known as Ragnarök, said event was destined to take place when the fire demon Surtur, empowered by the Eternal Flame, unleashed his rage upon Asgard and consumed it in fire.

In an attempt to prevent the fateful prophecy from being fulfilled, King Odin Borson confined Surtur to Muspelheim and locked the Eternal Flame in a vault beneath his palace.

Despite the Allfather's efforts, the people of Asgard believed that Ragnarök was inevitable, as made evident during a speech that would be delivered by Odin's son Thor towards the end of the Marauders' War.

A Prodigal Daughter
"We were unstoppable. I was his weapon in the conquest that built Asgard's empire. One by one, the Realms became ours. But then, simply because my ambition outgrew his, he banished me, caged me, locked me away like an animal."

- Hela Unbeknownst to all, Odin possessed a secret no one else knew about. Long before Thor was born, the Allfather had a daughter named Hela, who fought alongside him as his Chief Executioner and the leader of the Einherjar.

Hela played a key role in the creation of the Asgardian Empire, helping her father conquer the Nine Realms in a bloody and violent campaign. But Odin gradually began to see his daughter's overambitious nature as a threat to the peace needed to unite the Realms and, following a great battle, banished her to Hel for eternity.

Odin then went to great lengths to forget Hela ever existed, ordering that any mention or depiction of her role in Asgard's creation to be erased. Meanwhile, a resentful Hela started biding her time for the day when she would break free and exact vengeance against her father for his betrayal.

Journey to Muspelheim
"You cannot stop Ragnarök. Why fight it?" "Because that's what heroes do."

- Surtur and Thor

Troubled by a series of recurring dreams in which he saw the Fire Demon Surtur lay waste on Asgard, Thor journeyed to Muspelheim to avert this threat. He ended up captured and put in chains by Surtur, who explained that Thor had foreseen Ragnarök and that nothing, even Thor himself, could prevent this doomsday event from happening. Thor disagreed and broke out of his chains. After defeating a horde of Surtur's minions, Thor killed Surtur and seized his crown before escaping from Muspelheim. Once back in Asgard, the Crown of Surtur was stored in Odin's Vault.

Release of Hela
"So he's gone. That's a shame, I would've liked to have seen that."

- Hela

Having been told by Surtur that Odin was not on Asgard, Thor figured out that Loki, who he thought to be dead following the Second Battle of Svartalfheim, had usurped Asgard's throne and disguised as their father. Once the trickery revealed, Thor and Loki went to Earth to find Odin with Doctor Strange's help. Odin told his sons that he was dying and that his death would enable the Goddess of Death Hela to break free. After Odin vanished into Valhalla, Hela indeed appeared and easily destroyed Mjølnir. Panicked, Loki ordered Skurge to bring them back to Asgard, but Hela followed them and during the transport she cast out her brothers who fell on the distant planet of Sakaar. Arriving at the Bifrost Bridge, Hela killed Volstagg and Fandral and recruited Skurge as her right-hand man.

New Queen of Asgard
"It's come to my attention that you don't know who I am. I am Hela, Odin's firstborn, commander of the legions of Asgard, the rightful heir to the throne and the Goddess of Death! My father is dead. As are the princes. You're welcome."

- Hela

Hela made her way to the Asgardian Palace, where she was confronted by a company of Einherjar led by Hogun. Hela easily overpowered them and killed them one by one before entering the Palace and revealing Asgard's true history. Needing an army to resume her conquests, she went down to Odin's Vault and reclaimed the Eternal Flame, using its power to revive her Berserkers and her wolf Fenris. Hela intended to lead her soldiers across the Nine Realms and beyond, but quickly discovered an hindrance in her plan: Heimdall, the previous Gatekeeper, had stolen Hofund, keeping her from leaving Asgard. Hela ordered her men to chase the rebels and to find the sword. Meanwhile, Heimdall managed to hide dozens of Asgardians in abandoned strongholds.

An Asgardian agreed to disclose the location of the sword so that Hela would not massacre them one by one, prompting the Goddess of Death to leave the Palace with Skurge. However, once they arrived, the place was empty as Heimdall led the Asgardians to the Bifrost Bridge so that they could flee Asgard.

Thor's Return
"I would love for someone else to rule. But it can't be you. You're just the worst." "Okay, get up. You're in my seat."

- Thor and Hela

Meanwhile, Thor eventually made it out of Sakaar, founding the Revengers in the process. With their help, Thor made it to the Asgardian Palace, where he reclaimed Gungnir and knocked the ground of the throne room with it, attracting Hela's attention. Hela returned to the Palace and the two siblings entered in a violent Duel in the Asgardian Palace during which Thor lost an eye. In the end, Thor eventually mastered the full extent of his powers and used it to throw Hela out of the Palace.

Battle of the Rainbow Bridge
"No one's going anywhere. I'll get that sword, even if I have to kill every single one of them to do it."

- Hela to Thor

While Thor and Hela were fighting in the Asgardian Palace, a battle erupted on the Rainbow Bridge as the fleeing Asgardians led by Heimdall were trapped between Fenris on one side and the Berserkers led by Skurge on the other side. As the Asgardians were being attacked, reinforcements came to them: Loki led the Sakaaran Rebellion while Hulk fought against Fenris. Valkyrie also joined the battle and defeated many Berserkers. While the battle raged on the Bridge, the Asgardians boarded the Statesman brought by the Sakaaran Rebellion in order to escape to safety.

Thor ultimately released his full power, enabling him to join the battle and help his allies defeat the remaining Berserkers. Skurge eventually turned on Hela and killed many Berserkers as well before being slain by Hela. The Statesman ultimately took off the Bifrost Bridge. However, Hela was still alive and seemed invincible to the Revengers.

A Prophecy Fulfilled
"Tremble before me, Asgard. I am your reckoning!"

- Surtur

As Hela was approaching, Thor figured out that he had been mistaken all along: he was not supposed to prevent Ragnarök, but instead had to cause it as it was the only thing which could stop Hela. While he and Valkyrie fought the Goddess of Death, Loki went to Odin's Vault and put the Crown of Surtur in the Eternal Flame, reviving the Fire Demon with his full might. Surtur began laying waste on all Asgard, and although Hela tried to stop him, she was ultimately destroyed by the gigantic Twilight Sword. Meanwhile, the Revengers boarded the Statesman and watched as the planet was entirely destroyed, fulfilling the prophecy of Ragnarök.

Aftermath
"Earth it is."

- Thor

The loss of Asgard turned the Asgardians into a wandering people. Having been rescued thanks to the Sakaaran Rebellion and its Statesman, the Asgardians, led by their new King Thor, went in search of a new place to settle, and Thor decided to take them to Earth to build a new Asgard. However, on their way they met the infamous and gigantic spaceship known as the Sanctuary II, owned by none other than the dreadful Thanos. Thanos and the Black Order boarded and attacked the Statesman in order to extract the Space Stone, which Loki took from the vault prior to Asgard's destruction. Half of the Asgardians who survived Ragnarök died in the massacre, while the remaining others escaped, aided by Valkyrie.

Trivia

 * In the comics, Ragnarök was not a singular event, but an eternally recurring cycle of death that saw the cyclical destruction and subsequent revitalization of Asgard a countless number of times. The latest Ragnarök event was caused by a major battle between Asgard's people and an army of soldiers led by Loki utilizing copies of Mjølnir. The resulting battle obliterated Asgard, and the survivors settled on Earth in Broxton, Oklahoma.
 * In the non-canon video game Thor: God of Thunder, Odin uses the Odinforce to revive Sif after she is killed by a Frost Goliath, believing that it will prevent Thor from starting another war with the Frost Giants. Loki tells Odin that Thor will defy him and wage war against the Jotuns until Ragnarök.