In ancient myth, Hippocamps (aka Sea Horses) were known to be under Poseidon’s dominion, as he is God of the Sea, and of Horses. In some depictions the Sea Horse is seen as what pulls Poseidon’s undersea chariot.
Baian first appeared in volume 14 of Saint Seiya as the Marine General who is protecting the North Pacific Pillar. He was the first of the Marine Generals to be challenged by a Saint in order to protect his Pillar. He had to face off against Seiya, and at first was successful, blocking all of his attacks, and knocking him away, and even through the entire Ocean with powerful attacks. But, his secret was quickly discovered by Seiya, and Baian was last seen with a broken Scale, falling to Seiya’s attacks.