Thor once strained to lift an ordinary house cat and could raise only a single paw, not knowing the cat was an illusion hiding the Midgard Serpent, and that pulling harder would have snapped the boundaries of the universe. This episode builds a biography of Jormungandr, the middle child of Loki and Angrboda, from Odin's attempt to kill him by hurling him into the ocean, to his growth into the world-encircling serpent biting his own tail, to his role as the literal bind holding Midgard together.

It follows Thor's obsessive vendetta through the famous fishing trip with the giant Hymir, where an ox head is used as bait and Thor's feet punch through the boat, and compares the Prose Edda's version with Viking-age runestones that show different endings. It concludes with Ragnarok, the mutual destruction of Thor and the serpent, the significance o ...