Loki's children. Sleipnir, Fenrir and Jormungand

Sleipnir ("sliding" or "lively, agile, nimble") - in German-Scandinavian mythology, Odin's eight-legged horse, the offspring of Loki.
Jormungand or Midgardsorm is a sea serpent that was thrown into the ocean surrounding Midgard. The serpent grew so huge that it girdled the entire Earth and clung to its own tail. In Ragnarok, Midgardsorm and Thor, being eternal opponents, kill each other.
Fenrir is a huge wolf, the son of Loki and Angrboda. The enemy of the gods, Fenrir was the youngest of Loki's children. Initially, the gods considered him not dangerous enough and allowed him to live in Asgard. The wolf grew up among the aces, and became so large and terrible that only Tyr, the god of military courage, dared to feed him. To protect themselves, the Aesir decided to chain Fenrir with a chain, but the mighty wolf easily tore the strongest chains (Leding and Drommy). In the end, the aces by cunning still managed to bind Fenrir with the magic chain Gleipnir, which the dwarves made from the noise of cat steps, a woman's beard, mountain roots, bear veins (in ancient times, tendons were attributed to the properties of nerves), fish breath and bird saliva. All this is no longer in the world. Glaipnir was thin and soft as silk. But in order for the wolf to allow him to put on this chain, Tyur had to put his hand in his mouth as a sign of the absence of evil intentions. When Fenrir could not free himself, he bit off Tyr's hand. The Aesir chained Fenrir to a rock deep underground, and stuck a sword between his jaws. On the day of Ragnarok, according to the Völva's prophecy, Fenrir will break his bonds, kill Odin and himself will be killed by Vidar, the son of Odin.