The White Dragon Horse is the transformed dragon prince who carries Tang Seng on the journey for scriptures. He is a person under discipline who serves in the form of a mount, not an ordinary horse purchased for travel.
In chapter 15, the dragon of Eagle Sorrow Stream consumes Tang Seng’s first white horse. Guanyin identifies him as the dragon assigned to the pilgrim, removes his dragon features, and changes him into a horse. Chapter 100 restores his dragon body and gives him a sacred office after the pilgrimage succeeds.
The horse form embodies sustained service: he bears the pilgrim and the mission across the road while usually remaining quiet within the group. His identity requires both forms to be remembered. He is distinct from the published White Ox True Form, which is Bull Demon King’s own body rather than a mount.