Acquire special horse feed used for feeding a spirit horse.  Merideth Carlson in Southshore apparently is the source for such food.$B$BTravel to the Dire Maul dungeon in Feralas and slay Tendris Warpwood.  Doing so will free the Ancient Equine Spirit.  Feed it the special horse feed, thereby soothing the spirit.  Finally, give it the Arcanite Barding so it may bless it.