Midgard is a realm in Norse mythology. Pictured as placed somewhere in the middle of Yggdrasil, Midgard is surrounded by a world of water, or ocean, that is impassable. The ocean is inhabited by the great sea serpent Jörmungandr (Miðgarðsormr), who is so huge that he encircles the world entirely, grasping his own tail. The concept is similar to that of the Ouroboros.
Sleipnir It was Odin's gray eight legged horse. The horse was a magical horse, and the best of all horses. Sleipnir is the symbol of the wind, and has the marks of hell. Sleipnir could just as easily gallop through the air as on land. Sleipnir was a gift from Loki. Sleipnir is the child of Loki and Svadilfari.