Svipdagr (Old Norse "sudden day") is the hero of the two Old Norse Eddaic poems Grógaldr and Fjölsvinnsmál, which are contained within the body of one work; Svipdagsmál.
Svipdagr is set a task by his stepmother, to meet the goddess Menglöð, who is his "fated bride." In order to accomplish this seemingly impossible task, he summons by necromancy the shade of his dead mother, Gróa, a völva who also appears in the Prose Edda, to cast nine spells for him. This she does and the first poem abruptly ends.
At the beginning of the second poem, Svipdagr arrives at Menglöð's castle, where he is interrogated in a game of riddles by the watchman, from whom he conceals his true name (identifying himself as Vindkald(r) "Wind-Cold" apparently hoping to pass himself off as a frost giant). The watchman is named Fjölsviðr, a name of Odin in Grímnismál 47. He is accompanied by his wolf-hounds Geri and Gifr. After a series of eighteen questions and answers concerning the castle, its inhabitants, and its environment, Svipdagr ultimately learns that the gates will only open to one person: Svipdagr. On his revealing his identity, the gates of the castle open and Menglöð rises to greet her expected lover, welcoming him "back" to her.