The Casket of Ancient Winters is an ancient Asgardian artifact that contain the infinite cold from Niffleheim, the realm of the dishonored dead. It was hidden by Odin long ago in Midgard, where no one knew where it is. Once it is unleashed, it will not stop for all eternity until it's closed by someone who's brave enough to stand the extreme cold.
The casket was located and found in Norway when Malekith (in disguise) led a group of travelers to an ancient Viking fort which the others ran off and the other got frozen in ice trying to open the box where the Casket is inside.
Malekith then used the Casket to engulf the world in ice in his plans to bring back his dead people, the Dark Elves and cut off Midgard from the Nine Realms and make it their new home.
But his plans were stopped by Iron Man, Thor, and Black Panther. Before they celebrate, the trio were magically tied up by the Enchantress who took the Casket and left with her Executioner through their portal.
- ↑ 1.0 1.1 1.2 1.3 "The Casket of Ancient Winters". Paul Giacoppo (writer) & Sebastian Montes (director). The Avengers: Earth's Mightiest Heroes. May 15, 2011. No. 20, Season one.
- ↑ "The Fall of Asgard". Christopher Yost (writer) & Vinton Heuck (director). The Avengers: Earth's Mightiest Heroes. June 19, 2011. No. 25, Season one.