Balius and Xanthus

In other traditions, Poseidon is the father of Xanthus along with another horse named Cyllarus to an unnamed mother.

Peleus later gave the horses to his son Achilles who took them to draw his chariot during the Trojan War.

Sarpedon, prince of Lycia and ally of Troy, killed Pedasos when his spear missed Patroclus.

When Xanthus was rebuked by the grieving Achilles for allowing Patroclus to be slain, Hera granted Xanthus human speech allowing the horse to say that a god had killed Patroclus and that a god would soon kill Achilles too.

The latter bestowed them onto the Dioscuri to use as their horses in battle, and Xanthus retains his ability to speak with Castor.