Horse was an unusual stallion ridden by Eriond. He had the capability to jump though space, a power described by Eriond as entering a different dimension, then reappearing where he wanted to go. He was born as a colt in Magician's Gambit, and was stillborn. Garion resurrected him in the Cave of the Gods, and the colt was at first very attached to Garion. Later on, Garion took him to Riva, then gave him to Eriond, professing his inability to care for Horse.
In the King of the Murgos, Horse was able to carry Garion over a large distance which should have taken two days in a half hour.