Centuries ago Malekith proved himself to be an enemy of both the humans of Earth and the gods of Asgard. Malekith's greates weapon was the Casket of Ancient Winters, which contained mystical forces that could reproduce the overwhelming frigidity of another of the Nine Worlds, Niffleheim, the realm of ice. To prevent Malekith from releasing the contents of the casket, Eric Willis, a mortal man, stole the casket. Without the caskets power Malekith was unable to protect himself from the wrath of Odin, the All-Father, Ruler of Asgard. Odin banished Malekith to another dimension where he remained for centuries, until he was freed in recent times by the fire demon Surtur, ruler of Muspelheim, who became Malekith's master.
Surtur's first command was for Malekith to regain the Casket of Ancient Winters so it could be used on Earth, to usher in the Invasion forces of Muspelheim. Odin dispatched his ravens Huginn and Muninn to spy on the forces of Muspelheim. Huginn was murdered by Surtur, and Muninn was injured. Malekith tried unsuccefully to prevent Muninn from escaping. Shortly after this Malekith was ordered by Surtur to form an alliance with Loki. The alliance was meant to ensure that Loki would not aid the forces of Asgard. Knowing thqat Surtur intended to destroy Asgard Loki deceived Malekith and had no intention of watching Asgard fall. The magic from the Casket had preserved Eric Willis and he was still the same age as when he stole it.
Malekith had his human agents harass Eric, in an attempt to regain the Casket, this evetually lead to his being murdered by Malekith himself. The Casket was recovered by Willis son Roger. Tired of being denied his prize; Malekith summoned the Wild Hunt, a pack of demonic hounds, to track Roger Willis. But was eventually defeated and presumed dead after Kurse had broken his neck.
However,Malekith only feigned his death would return years later,disguising himself as Balder, and tricked Hercules to attack Alflyse, the Dark Elf Queen of the Eastern Spires, while Hercules was dressed as Thor. His scheme unraveled (partially due to the appearance of Thor disguised as Hercules), and he was struck down by Zeus, beaten again, he has not been seen since then.
In Other Media
The Avengers: Earth's Mightiest Heroes
Malekith appears in the episode "The Casket of Ancient Winters" voiced by Quinton Flynn. He is shown to be working with Enchantress and Loki to obtain the Casket of Ancient Winters before betraying them in order to use the casket to resurrect his people, the Dark Elves, as well as bring about an endless winter on Earth. He is defeated through the combined efforts of Iron Man, Black Panther and Thor when Iron Man uses his metal suit as a superconductor to channel Thor's mystical lighting through the Dark Elf. It is presumed that Malekith perished in the ensuing battle, but given the undead nature of his character that remains to be seen.
Thor: The Dark World
Malekith the Accursed is played by Christopher Eccleston in the sequel to the Thor movie. He leads the Dark Elves to war in order to obtain the Aether (one of the Infinity Stones) and return the universe to a state of darkness so his race may rule again. He attempts to extract the Aether from Jane Foster's body, but is outsmarted and eventually defeated by Loki and Thor. He is apparently killed after being crushed to death by one of his ships.