Onyx is a warrior blacktip reef shark. He has mysterious tattoos that came from his time with Indi Shiver, which is unknown to Gray. He revealed that he once knew Finnivus and when they were out hunting together, Onyx broke the royal rule of letting the prince make the first kill. He participated in and survived the Battle of the Maw. In the fourth book, it was believed that he was killed by Hokuu's fireball. It was revealed in Enemy of Oceans that he survived.