in the comic back in the day, malekith did the same thing, only with Balder. since he was a known sorcerer and shape shifter, they had 'malekith' gagged and bound in rune chains to stop him from communicating or using any magic and put him in a deeeeeeep dark hole. he was eventually outted by Kurse/Algrim, who was responsible for turning him into an unstoppable juggernaut after thor beat his ass and fried him krispy in lava, anakin-vader style. since the malekith/algrim storyline's been altered in the movie (and balder's not even mentioned), i'm betting for something similar just with loki/odin.