Complex sentence: According to the "Prose Edda", Odin took Loki's three children, Fenrisúlfr, Hel and Jörmungandr, and tossed Jörmungandr into the great ocean that encircles Midgard.
Split into simpler sentences: According to the "Prose Edda", Odin took Loki's three children, Fenrisúlfr, Hel and Jörmungandr. He tossed Jörmungandr into the great ocean that encircles Midgard.