Marvel has recently confirmed that Thor villain Loki (Tom Hiddleston) will be reprising his role in the upcoming Avengers film, which is good news for me as watching Thor recently he was one of the best actors in it and fitted perfectly into the role of the god of mischief. The Avengers director Joss Whedon has also confirmed that Erik Selvig (Stellan Scarsgard) will also be returning.
THOR SPOILERS! At the very end of Thor Loki uses Erik to take a magical cube from Nick Fury (Samuel L Jackson), which is most likely the Tesseract as seen in the Captain America trailers being held by the Red Skull and is ultimately his tool in which he plans to take over the world with. Seeing as Loki is obtaining this great source of power I can only imagine that he will be the main villain in the upcoming Avengers flick, but what he is going to conjure up with said device I can only wonder.