The Jotunheim Beast is an animal native to the planet Jotunheim. It is massive in size and can run at incredible speeds. It can be frozen solid for long periods of time.
One of these beasts was awakened from his deep slumber by Laufey to kill Thor, Loki, Sif, and The Warriors Three for intruding in his realm.
It was soon killed by Thor, who propelled himself through its head.
Another beast was disturbed by Thor and Malekith's battle through the portals of the Convergence. It wound up in London, where it rampaged through the city for at least two days.