The stock of horses wandering the Wanda Plains from which Damian Frost chooses those special horses for training as mounts for the Green Rider corps. In HKT, Karigan and Fergal deliver an order for more horses and get to witness the wild horses greet their lord Salvistar, the steed of Westrion. It is likely that the Rider horses are especially favoured by Salvistar as they have demonstrated an uncanny intelligence throughout the series.

Green riderEDIT

Picture from the front of Green Rider book. The horse is a Green Rider mount, especially picked for Green Riders.