Fenrir
The god Tyr tamed and bound the wolf Fenrir (Fenris Wolf), losing a hand in the process. He bound him with a chain that was crated by dwarves from the roots of a mountain, the noise of a moving cat and the breath of a fish. This chain is as thin and delicate as silk but unbreakable.
Fenrir is destined to stay bound in the chain until the Ragnarok when it is believed that he will slay Odin and then be killed hmself. Sometimes this legend is described as Fenris wolf eating the sun (odin being a personification of the sun).
Adapted from 'A guide to the Gods' by Richard Carlyon