Here is a comprehensive summary of the Wikipedia article on Loki:

Loki is a prominent trickster god in Norse mythology, famously engineering the death of the beloved god Baldr, for which the gods bound him to a rock with his mouth stitched shut. While imprisoned, his faithful wife Sigyn catches the dripping serpent venom in a bowl, but whenever she empties it, Loki writhes in agony, causing earthquakes. As a shape-shifter, he is a son of the jötunn Fárbauti and goddess Laufey, and is the father of the monstrous Hel, the wolf Fenrir, and the world serpent Jörmungandr—as well as giving birth to the eight-legged horse Sleipnir after being impregnated by a stallion in the form of a mare. Foretold to break free during Ragnarök, he will battle the gods and have a fatal mutual kill with his archenemy Heimdallr, leading to the destruction of humanity. His story is primarily attested in the 13th-century Poetic Edda and Prose Edda (compiled by Snorri Sturluson), and scholars debate his origins, though his name likely stems from the Germanic root luk- meaning "loops and knots," reflecting his role as a tangler of fate rather than a fire god.