The sand steed is a type of horse bred in Dorne.
The horse is marked by its long neck, narrow head and its slimness and swiftness. They have narrow, beautiful heads. Some sand steed colours are red, golden, black and pale as snow. They are smaller than normal warhorses and cannot bear the weight of the armor a warhorse usually wears. Dornishmen claim the mounts are able to run for a day and night and another day, and never tire.
In The Conquest of Dorne King Daeron I Targaryen remarked that the Dornish love their sand steeds equal to their children, and wrote that the Knight of Spottswood had his sand steeds stabled in his very own hall.
A Storm of Swords