Warning: possible spoilers for Thor: Ragnarok ahead.
"Ragnarok" isn't just a funny-sounding term they added to the third Thor installment's title to make it sound more mystical. Within Norse mythology (from which Thor, Loki, Odin, and their fellow Asgardians spring), Ragnarok is known as "the War of the Gods" or, even more ominously, "the Doom of the Gods."
At its most basic, the Ragnarok is the Norse apocalypse — but there's a slight twist. Unlike in other cultures' takes on the end of the world, the gods are in for it, too, right alongside their mortal subjects. The myth's source materials, including the Icelandic poem Völuspá and the Nordic text the Prose Edda, describe a period of cold and decline preceding the Ragnarok itself, sometimes referred to as the "Awful Winter."
The story goes that three long winters befell the world of gods and men, one following the other, while moral decency all but fell away, driving people to act only out of greed and bloodlust. It was at this time that the gods' enemies, from wolves to giants to dragons, joined forces to overtake and destroy the world.
Some versions describe a massive wolf swallowing the sun, while others mention troll women ravaging the earth. Across the many retellings and translations of this story, the end remains consistent: All the gods — yes, even Thor and Loki — die heroes' deaths in the melee, the sun goes out, and the world sinks into the sea.
Suffice it to say, Asgard isn't in great shape by the end of Thor: Ragnarok. But don't let this dash your hopes of yet another Thor film: The massive destruction of Ragnarok is followed by a period of creation. Author Daniel McCoy writes that time in Norse mythology is cyclical — not linear. So, as soon as the end times come, life can begin again. And that might just be a teaser for the would-be sequel Ragnarok director Taika Waititi has been hinting at.