Details of Surtur's origin are unknown. Presumably he was born and raised in Muspelheim, the land of the fire giants. At some point he became the ruler of Muspelheim.
Surtur is a fire giant from Norse mythology.
Major Story Arcs
Surtur has his first meeting with Odin when the young god and his brothers, Vili and Ve, travel to Muspelheim to speak with him. During this conversation, Surtur confirms that he will destroy the world in fire using his Twilight Sword and the Eternal Flame of Destruction. When Odin suggests that the Flame should be extinguished and the sword broken, Surtur has him and his brothers attacked by fire demons. The trio merges into one being to fight Surtur, who nonetheless easily holds them off. They manage to destroy his sword, and cut the Flame. Odin flees when Surtur begins to recover, but finds his brothers have remained behind. Surtur kills them both.
Surtur attempts to stir up a rebellion against Asgard. Finding he cannot hurt Odin, he attempts to hurt him indirectly by attacking the Earth. He burrows into the center of the Earth, sending up a fragment of the rock which becomes the Moon. Odin sets the Earth spinning, causing Surtur to become trapped in the center of the Earth. Surtur sends Odin a winged horse as appeasement, but remains trapped.
Still trapped in the center of the Earth, Surtur is contacted by Loki, who proposes they join forces to attack Asgard. Loki offers his mentor Eldred's soul to Surtur, so long as Loki is allowed to absorb Eldred's power. Surtur agrees to this plan, and Loki is able to convince Eldred to summon Surtur, setting their plan in motion. Later, Loki is left in charge of Asgard by Odin. Using his new powers he frees Skagg, a storm giant, and Surtur. When the Asgardians attempt to mount a defense against the giants, Surtur attacks Thor and rescues Skagg from Odin. Later, he attempts to melt the ice caps in order to flood the Earth. He is defeated when Thor traps him on an asteroid.
Spell of Fire and Ice
Surtur is summoned alongside Ymir, a frost giant, when a dying Asmodeus casts the Spell of Fire and Ice. Surtur and Ymir arrive on Earth and begin wreaking havoc. He is confronted by members of the Avengers, but they are hopelessly outmatched. He is defeated when he and Ymir are tricked into striking one another, cancelling out their respective powers and returning them to their home dimensions.
Surtur attacks Asgard, the throne of which has recently been usurped by Loki. Loki flees and Thor is left to battle Surtur with the Asgardian forces. He attempts to fight Surtur single-handedly, but fails, as do all other attacks. Surtur is defeated when Odin returns and traps him in the Earth.
Cask of Ancient Winters
Surtur begins to reforge his sword, which had been broken centuries previous by Odin and his brothers. He forms an alliance with Malekith and Loki, and rouses the fire demons to fight alongside him. Under his direction, Malekith recovers the Casket of Ancient Winters, which he uses to spread chaos to herald Surtur's arrival. Surtur attempts to locate the Rainbow Bridge so he may attack Asgard, eventually managing to find it after tricking Thor into revealing its location. Thor and Surtur engage in a battle which is interrupted by the arrival of Odin. He and Odin fight, and he eventually manages to freeze Odin in a ball of ice. He enters Asgard and attempts to set his sword ablaze in the Flame. However, the Flame was an illusion created by Loki, who then attacks Surtur. The pair fight for some time, but Surtur is able to overwhelm him and locate the real Flame. Before he is able to use it he is confronted by Thor, Odin, and Loki, who together manage to defeat him, at the expense of trapping Odin in a fissure alongside him.
The Endless Circle
Odin is captured shortly after they fall, and Surtur is prevented from locating him due to power dampeners. These are removed, and Surtur attempts to attack. In Odin's place he finds Thor, whom he fights. Thor is eventually able to render Surtur unconscious, and, reflecting that Surtur could escape from any prison, Odin absorbs Surtur's essence. Sometime later, Odin begins behaving erratically. He notes that the final cycle of the Endless Circle is beginning, and that Ragnarök is coming. Eventually he reveals that he has become merged with Surtur, who emerges and attacks the newly arisen Ymir due to Odin's influence over him. Thor lights the Twilight Sword because it is the only way to destroy Surtur or Ymir. The lighting of the sword causes Odin to lose his control over Surtur, who joins forces with Ymir. The pair attempt to reclaim the Twilight Sword, but cannot agree over who should wield it, and turn on each other. While they are distracted, Thor opens a portal to the Sea of Eternal Night and traps the pair there in suspended animation.
A medallion apparently related to Surtur is discovered by fishermen off the coast of Norway. By that evening almost every member of the crew is dead, and the lone survivor appears to have been corrupted by the influence of the medallion. He sacrifices himself in flame and emerges as a fire being. The village is destroyed, and villagers enslaved. Surtur returns to the Earthly plane, proclaiming his need to bathe the world in cleansing fires. He fights Thor and his heroic companions. He is apparently defeated by Odin, who also disappears in the blast created by his attack.
Surtur is trapped in Limbo forced to survive of the flesh of demons, which are kept sparse by Balder and his knights whose mission is to slave any demons that sneak into Limbo before Surtur can get them. Surtur is able to find and devour Hel Wolf and then he discovers Loki, who had died and been brought back by Thor as an innocent child. Surtur doesn't trust this new Loki but makes a deal with him anyway.
He lends Loki Twilight swords opposite and in return Loki promises Surtur Asgard. When Surtur breaks out of Limbo to collect his payment he finds himself aboard The Serpent's Dark Asgard. Loki had tricked him but he was now free and feasted upon Asgard's heart, just not the one he felt he was promised.
After having been freed from his exile in Limbo by Loki, Surtur makes a treaty with the Manchester Gods on Otherworld which entails Surtur would supply them power in form of a mystical artifact called "Engel -Craft" and in return they would act as a conduit to Surtur, without knowing about it, so when he finally releases his energy , the energies would vent through otherworld burning the multiverse in the process.
The rise of Surtur burns the world tree with a kind of fire never seen before. Thor tries everything to put the fire off, including rain and hail, but all attempts fail. Thor himself is burned by the fire, which is surprising given Thor has been shown to have casual conversation in the core of the Sun with Atum.
When Loki confronts Surtur seeking the shadow of the twilight sword, and in return would hand over Thor to him, Surtur explains his plans in details but accepts the deal with Loki giving him the shadow of the Twilight Sword.
Surtur is finally confronted by Thor and the Asgardian army all of whom seem utterly helpless against him. Meanwhile Loki travels to the Otherworld to explain to Manchester god what Surtur truly plans. Upon hearing the dread plan of Surtur and refusing to be a part of it, Manchester god willingly relinquish their dominion on the Otherworld, seemingly killing themselves in the process. This severs the Surtur conduit.
Even without the Manchester God Surtur evidently had enough energy in him to burn the 9 worlds. Loki teleports back to Surtur's realm and merges the shadow of the twilight sword with Mjolnir giving Thor the perfect weapon to defeat Surtur. Problem being even if they manage to defeat Surtur they don't have a way to deal with the vast energy Surtur has collected.
Loki and Leah pretending to be Freyja call Odin from his exile, The Dark Asgard, in order to help Thor. When Thor finally kills Surtur using the Twilight sword and the fire to unmake the universe is released, Odin manipulates and sends the fire through a portal behind him (presumably the same portal Odin used to come from The Dark Asgard). Surtur is defeated and Odin re-exiles himself.
Being purely elemental, death has never been permanent to Surtur so it's very likely he will show up again.
Powers and Abilities
Surtur is a fire giant of immense power; he is over 1,000 feet tall, possesses a prehensile tail, and is capable of controlling fire, as well as being composed largely of fire. He is extremely strong, immortal, and nigh-invulnerable, as well as possessing a capacity for molecular manipulation that allows him to become intangible or to shift parts of his body into other forms. He is capable of levitation and inter-dimensional travel. He is incredibly intelligent, and a gifted fighter, having special skill with a sword.
He possesses the Twilight Sword, a magical sword of unknown metal that can be wielded to many magical effects as well as in the traditional way one might use a sword. When lit with the Eternal Flame, the sword heralds Ragnarök and the end of the nine realms. Surtur has an unspecified connection to the Eternal Flame, and it appears to provide continuous strength to him when he is near to it. The mechanism for this, as well as the extent of the power he is capable of deriving from it, are unknown.
Surtur makes a cameo appearance in Amalgam Comics' Thorion of the New Asgods.
A member of Krona's army, Surtur fights Wonder Woman.
Surtur appears alongside Ymir in the Ultimate universe, and the pair invade Earth together. They are opposed by the Ultimate version of the Avengers.
Thor: Tales of Asgard
Surtur makes a cameo appearance in flashbacks. His sword, referred to as "Elderstahl," is the object of the film's major quest.
Spider-Man and His Amazing Friends
Surtur appears in the episode "The Vengeance of Loki". Iceman is teleported into his realm, and must be rescued by the ice giant Zerona.
Avengers: Earth's Mightiest Heroes
Surtur appears in several episodes, where he is portrayed as an antagonist who manages to take control of Enchantress. He is last seen reforging the Twilight Sword, presumably in anticipation of Ragnarok. He is played by Rick D Wasserman.
Marvel: Ultimate Alliance
Surtur makes a cameo appearance
Thor: God of Thunder
Surtur appears as an enemy who guards a type of heat-absorbing metal. He is played by Rick D Wasserman.
Marvel Super Hero Squad Online
Surtur appears as an enemy. He is played by John DiMaggio.