Four thousand years prior to the events in Tales of Symphonia, Kratos Aurion, the only human companion of Mithos Yggdrasill, traveled with him to put a stop to the long-lasting Kharlan War. Throughout his travels, Mithos formed pacts with each of the Summon Spirits and eventually had Origin, the King of Summon Spirits, create the Eternal Sword which Mithos used to split the world into two, creating Sylvarant and Tethe'alla. A seal based on Kratos was created to prevent anyone from gaining the power of the Summon Spirits, and it can only be broken once Kratos's mana is released, thus ending his life. Soon however, Mithos's sister Martel was killed, which sent Mithos into a deep grief. Misinterpreting her dying wish of a world without discrimination as a world where everyone is the same, he then went on to establish the Cruxis organization led by himself, Kratos and their companion Yuan Ka-Fai, who all became angels.
After learning about Mithos's plans for the Age of Lifeless Beings, Kratos descended upon Sylvarant. There he met a human woman named Anna, and the two fell in love, soon having a child: Lloyd Irving. Eventually, the Desian Grand Cardinal Kvar caught them, at which point Anna's Exsphere was removed and she became a mindless monster who attacked the infant Lloyd. After much hesitation, Kratos killed her in desperation to save his son. Kvar then attacked, causing Lloyd, Noishe, and Anna to tumble down a cliff near the Iselia Human Ranch. Believing his family to be dead, Kratos lost all meaning in his life. He soon returned to Cruxis, where he aided Mithos, believing that the half-elf would reunite the two worlds after Martel was revived.
During the events of Tales of Symphonia, Mithos sends Kratos to watch over Sylvarant's Chosen One, Colette Brunel, and make sure she does not stray from the Journey of Regeneration. He appears to Lloyd, Genis, and Colette and introduces himself as a mercenary, at which point he is hired to protect Colette. When the party travels to Dirk's house so she can speak to Lloyd, Kratos sees Anna's grave. It is at this point that he realizes that Lloyd is his son, though he hides it from the party. Once the party reaches the Tower of Salvation, Kratos reveals himself as an angel of Cruxis. Although he acts as their enemy, their actions over the course of the game slowly convince him of how much control of his destiny he really has, leading him to side with them. He breaks the seal after a duel with Lloyd and gives him his Flamberge to fight Mithos with.
In the Super Smash Flash series
In Super Smash Flash 2
This section contains information of a formerly confirmed feature.
The original source that confirmed the subject has otherwise become obsolete, outdated or deprecated and has yet to be re-confirmed by an official modern source.
Kratos was previously confirmed in Super Smash Flash 2 as part of the initial roster for the game. However, following the release of v0.7 of the SSF2 Demo, the developers revamped the whole roster in order to accommodate some new, unexpected characters. Currently, Kratos's fate as a playable character is unknown.