Loki

The wolf was still growing, and the gods were in the smithies, forging a new set of chains. Each link in the chains was too heavy for a normal man to lift. The metal of the chains was the strongest metal that gods could find: iron from the earth mixed with iron that had fallen from the sky. They called these chains Dromi.

[...]

"If you can escape these chains," said the gods, "then your renown and your strength will be known to all the worlds. Glory will be yours. If chains like this cannot hold you, then your strength will be greater than that of any of the gods or the giants."
Fenrir nodded at this, and looked at the chains called Dromi, bigger than any chains had ever been, stronger than the strongst of bonds.

[...]

The great wolf stretched and strained, but the chains held. The gods looked at each other, and there was the beginning of triumph in their eyes, but now the huge wolf began to twist and to writhe, to kick out his legs and strain every muscle and every sinew. His eyes flashed and his teeth flashed and his jaws foamed.
He growled as he writhed. He struggled with all his might.
The gods moved back involuntarily, and it was good that they did so, for the chains fractured and then broke with such violence that the pieces were thrown far into the air, and for years to come the gods would find lumps of shattered shackles embedded in the sides of huge trees or the side of a mountain.

[...]

And Fenris Wolf grew huger and hungrier with each day that passed.