Gleipnir

When the Fenrir wolf was to be chained up, the Norse gods first tried the chain Løding, but it broke. Then they tried with the chain Drome, which was twice as powerful. It went as badly.
 
Then Odin sent Skirne to the dwarfs in Svartalvheimen to ask them to make them a chain that was strong enough. The chain Gleipne was made of six things that nobody can find: the breath of the fish, the woman's beard, the spit of the bird, the roots of the mountain, the sound of cat paws and the tendons of the bear. Therefore, these things do not exist today. Gleipne was thin and soft like a silk cord, but stronger than any other chain.

The god Ty also had to put his hand in Fanrir's mouth, as reasurence that the wolf would be freed again. Ty lost his right hand. Fenrir is tied on the island Lyngve in the lake  Åmsvarte, his mouth forced open by a sword. Fenrir will breake free when Ragnarok begins.