Sleipnir (pronounced “SLAYP-neer”; Old Norse Sleipnir, “The Sliding One”) is the eight-legged horse of the god Odin. Sleipnir is one of Odin’s many shamanic helping spirits, ranks that also include the valkyries and Hugin and Munin, and he can probably be classified as a fylgja. Odin rides Sleipnir on his frequent journeys throughout the Nine Worlds, which are held in the branches and roots of the world-tree Yggdrasil.
The eight-legged horse as a means of transportation used by shamans in their ecstatic travels throughout the cosmos is a motif that can be found in a staggering number of indigenous traditions from all over the world. Sleipnir is “the shamanic horse par excellence,” just as Odin is the shamanic god par excellence.
 Price, Neil S. 2002. The Viking Way: Religion and War in Late Iron Age Scandinavia. p. 320-323.