Chestnut
From A Wiki of Ice and Fire
Chestnut was an old horse, a stot[1] owned by Ser Arlan of Pennytree.
History
When Ser Arlan died, Duncan the Tall took ownership of Chestnut along with Thunder and Sweetfoot.[2]
Chestnut died in Dorne, during the desert crossing between the Prince's Pass and Vaith.[1]