British actor Eccleston is probably best known for his portrayal of the revitalized Doctor when Doctor Who returned in 2005, a run that extended over thirteen episodes. He also appeared in several episodes on the first season of Heroes before the wheels came off. On the feature side of things, though, Eccleston memorably portrayed an inflexible authority figure in 28 Days Later, and played villains in Gone in Sixty Seconds and G.I. Joe: The Rise of Cobra. He's a charismatic guy and one who conveys cold, calculated intelligence remarkably well.
So he should be well suited to play a Marvel bad guy. Presumably, the role Eccleston's playing is the same one for which Mads Mikkelsen was in talks before his commitment to star in the Hannibal Lector television series caused him to opt out. That's not confirmed, but Deadline does confirm that Eccleston is locked down into the role of Malekith the Accursed.
A rumor started by a stun performer's offhand remark back in June asserted that Thor would be facing off against the Dark Elves in this film, a rumor supported by the title. Eccleston's casting as Malekith the Accursed makes it certain, since Malekith is the leader of the Dark Elves, who inhabit Svartalfheim, one of the Nine Realms.
It's previously been reported that after villainizing Thor and The Avengers, Loki, played by Tom Hiddleston, would be up to some hijinks in Thor: The Dark World, but would not be the principal antagonist. That's Malekith's job, and since the superpowered head honcho of the Dark Elves has made alliances with Loki since his first printed appearance in 1984, Malekith has partnered up with Loki on a few occasions.
Christopher Eccleston joins Chris Hemsworth in his third turn as Odin's son and the god of thunder. Returning cast from the first film includes Hiddleston, Natalie Portman, Anthony Hopkins, Idris Elba, Stellan Skarsgard, Jaimie Alexander, Tadanobu Asano, and Ray Stevenson, along with Zachary Levi, who will be replacing Josh Dallas as one of the Warriors Three.
Frequent Game of Thrones helmer Alan Taylor is directing the sequel from a screenplay by Don Payne, who contributed to the first film, and Robert Rodat, best known as the writer behind Saving Private Ryan.
Thor: The Dark World is scheduled to arrive in theaters on November 8, 2013.