Frostgrinder

Frostgrinder is the Troll equivalent of the Bifrost Bridge.

History
As part of his quest to make himself look like the ultimate and greatest hero of Asgard, Loki sent his adoptive brother Thor to Nornheim, land of the Rock Trolls, where Thor battled Ulik. Contrary to his plans, Loki was forced to aid his brother in activating Frostgrinder, in order to escape, realizing Mangog was too powerful of an adversary. Upon their exit, Frostgrinder was destroyed.