Kratos Aurion is an immortal being and one of the Four Seraphim, a group of powerful angels. He was one of the founders of Cruxis and initially served directly under the god Yggdrasill. Throughout his life, Kratos played important roles in the history of the world of "Tales of Symphonia".

He fell in love with a human woman named Anna and had a son, Lloyd Irving. However, Anna was captured and killed by the Desians, leaving Kratos with the responsibility of protecting his son. This event shaped his actions and motivations, leading him to question his loyalties and seek redemption.

As a skilled swordsman and magic user, Kratos is a formidable combatant. He initially joins protagonist Lloyd's party as a bodyguard and mentor, but his true identity and intentions are revealed throughout the game. He struggles to right his past wrongs and protect those he loves.