History
Ages ago, Surtur, somehow, was imprisoned by the Seal of Borsons with the Norn Stones as protective barrier seals.[1]
After the destruction of the last Norn Stone, Surtur was released from his imprisonment then burned Nidavellir to the stone, killing almost all the dwarves and nearly destroying a supply of precious uru.
Surtur's conquest reaches throughout the Nine Realms, expanding far into space. Surtur takes full control of Amora, possessing her to lead an army of fire demons to conquer all worlds.[2]
After Thor learns of Surtur's release and of the disappearance of the Twilight Sword, he alerts Odin. Odin goes on his own to investigate the release of Surtur only to return with very little knowledge. When a ship is discovered in Midgard with the presence of Surtur, Thor, with the help of Heimdall, travels to the ship to learn of Surtur's plans. There Thor finds Beta Ray Bill, a survivor of Surtur's destruction of the Korbinite home planet.[3]
The Avengers Earth's Mightiest Heroes Surtur's Awakening
Surtur's first appearance and the gods find out that the barriers are broken