Dornish sand steed
From A Wiki of Ice and Fire
The Dornish sand steed is a type of horse bred in Dorne.
It 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.