Fenrir

Fenrir is the doom of the gods given fur and teeth. The monstrous wolf-child of Loki and the giantess Angrboða, he was reared among the Æsir themselves until the prophecies grew too loud to ignore: this creature would be their destruction, and would swallow Odin at the end of the world. They could not kill him in their sanctuary, and they could not hold him by strength — he snapped their greatest iron fetters like thread. Only by the dwarf-made ribbon Gleipnir, soft as silk and forged of six impossible things, could he be bound, and only by a trick: a god's hand in his jaws as a false pledge, which cost Týr that hand. So he lies gagged with a sword and chained to a rock, slaver running from his mouth in a river, until Ragnarök looses him to make good every prophecy at once. Fenrir is the Norse truth that the end is not an enemy at the gates but a thing raised at home, fed by your own hand, and only postponed.