 He still kept an eye on Calydonian politics (his father's homeland), and when the sons of Agrius (led by Thersites) put Oeneus (Diomedes’ grandfather) in jail and their own father on the throne, Diomedes decided to restore Oeneus to the throne.Diomedes attacked and ceded the kingdom, slaying all the traitors except Thersites, Onchestus (who escaped to Peloponnesus) and Agrius (who killed himself) restoring his grandfather to the throne.Later, Oeneus passed the kingdom to his son-in-law, Andraemon, and headed to Argos to meet Diomedes.