Loki the most complicated Norse character and the giantess Angrboda (“She who Brings Anguish”) had three notorious children. His first son was the Jormungandr the Midgard Serpent, the second daughter was Hel the Queen of Helheim, and the last one was Wolf Fenrir the God of Destruction.
Jormungandr was also known as the Midgard Serpent. He was cast into the deep ocean by Odin the Allfather as a precaution against the Ragnarok. Deep under the ocean laid Jormungandr who quickly grew large enough to encircle the whole Midgard. Jormungandr held his own tail in his mouth. He was the sworn enemy of Thor. These two (Jormungandr and Thor) had encountered each other once before the days of Ragnarok.
As Ragnarok was looming large, Jormungandr raised from the ocean and accompanied Loki’s army to enter Asgard. This Midgard Serpent had his last battle with Thor and got killed by the blow from Mjölnir hammer. Thor, unfortunately, was slain by the venom of the dead Jormungandr.
The only daughter of Loki, Hel, was banished into the land of Helheim located deep under the root of Yggdrasil tree. There, Hel built up her own kingdom of the dead and presided over that place. She was the queen of the deceased and the land of Helheim. According to the myth, if one soul belonged to Hel, without her permission, that soul could not do anything but serve in the land of Helheim. No one could ever interfere with this practice, even Odin the Allfather.
Hel joined the army of the Jotun to battle against Aesir gods. She brought the dead alongside.
Hardly could any villain in Norse myth rival the reputation of Wolf Fenrir. Fenrir was the worst nightmare to the Norse gods because Fenrir was predicted to swallow Odin in Ragnarok. As the gods scared that this scenario would come into being, they decided to raise the wolf by themselves. When the wolf grew up at an incredible speed, they bound Fenrir with a magical fetter. Fenrir then was sent to a middle-of-no-where place until he broke free on the threshold of Ragnarok.
In Ragnarok, Fenrir and his father, Loki, led the giant army to fight against the gods. Fenrir opened his enormous mouth with his jaw stretching from heaven to earth and swallowing anything that hindered him. When battling with Odin, Fenrir gained the upper hand and swallowed the god, proving the prophecy to be true.
Other Children of Loki
Sleipnir – Sleipnir was the result of one-night chase between Loki and a stallion Svadilfari. This happened when Loki wanted to prevent Svadilfari from finishing building Asgard Wall. Loki in disguise as a mare seduced Svadilfari to distract the stallion from finishing its task. As a result, a little horse was brought to life. Sleipnir was his name. And in fact, Loki was the mother of Sleipnir horse. Yes, Loki was the mother! Sleipnir horse then was given to Odin the Allfather by Loki. Sleipnir was a true treasure as he could travel not only on land but also over the sea and through the air. Odin rode Sleipnir into the battle of Ragnarok where he met Wolf Fenrir.
Nari and Vali – these two children of Loki had little material about them. The most well-known tale about these two was in the Punishment of Loki. The ironic story told that Vali in the form of a wolf killed his brother Nari. The gods used the entrails of Nari to bind Loki to the rocks as Loki’s most severe punishment for causing trouble to the gods.