Loki discovers that he is Laufey's biological son, adopted by Odin after the war ended. Loki confronts Odin, who wearily falls into the deep "Odinsleep" to recover his strength. Loki takes the throne in Odin's stead and offers Laufey the chance to kill Odin and retrieve the Casket. Sif and the Warriors Three, unhappy with Loki's rule, attempt to return Thor from exile, convincing Heimdall, gatekeeper of the Bifröst—the means of traveling between worlds—to allow them passage to Earth. Aware of their plan, Loki sends the Destroyer, a seemingly indestructible automaton, to pursue them and kill Thor. The warriors find Thor, but the Destroyer attacks and defeats them, prompting Thor to offer himself instead. Struck by the Destroyer and near death, Thor proves himself worthy by his sacrifice to wield Mjölnir. The hammer returns to him, restoring his powers and enabling him to defeat the Destroyer. Kissing Foster goodbye and vowing to return, he leaves with his fellow Asgardians to confront Loki.