King Agon was the king of Attilan, a city on the Moon populated by Inhumans. During his reign, Agon ordered the deaths of Ambur and Quelin, the parents of Medusa and Crystal. Agon and his wife Rynda were accidentally killed by their son Black Bolt after Terrigenesis gave him a powerful, destructive voice. His voice liquefied them both when he asked them why the Terrigen Mist would give him such a terrifying power. Black Bolt succeeded Agon as Attilan's king.