Supideo was a resident of the town of Opous in Lokris, Greece during the 5th century BCE. His adopted parents were Katina and Pedasos, but he was the biological son of Kosta, the village blacksmith and a bandit woman. Prophesied by the Pythia to be the cause of his mother's brutal death and his father screaming in agony, he attempted to defy fate, but unwittingly set them into motion owing to his ignorance as to his true parentage.
During the Peloponnesian War the Spartan misthios Kassandra was passing through the village when she overheard Supideo arguing with Katina and Pedasos, his adoptive parents. Stepping in, Kassandra learned that Supideo had visited the Pythia and was told by her that he would cause his mother's blood to stain the ground and his father to scream. This led to Supideo asking Kassandra to recover his sword and shield so that his parents could protect themselves. Supideo had given the sword to Kosta to sharpen whereas the shield had been stolen by a woman from the bandit camp by the Red Lake; he was not aware that these two individual were, in fact, his real parents.
Kassandra managed to retrieve the sword and the shield, momentarily setting Supideo's mind at ease until he discovered from his adoptive parents his true parentage and that, in the mercenary's interaction with Kosta and her slaying of the bandit, they had unwittingly fulfilled the prophecy.
- Supideo's name and the prophecy detailing his parents' fate are both a parody and an homage to those same elements in Sophokles' play Oedipus Rex. His name is an ananym of the play's eponymous tragic hero, Oedipus, who the Oracle of Delphi prophesied would kill his father Laios and sleep with his mother Jocasta. Attempting to avert fate, Jocasta ordered a servant to abandon the child in the hills, but unbeknownst to her, the man instead passed the baby to a shepherd, who in turn passed it to another shepherd. He soon arrived at the doorstep of King Polybus and Queen Merope of Korinth, who took him in and raised him as their own, thereby setting in motion the prophecy's eventual fulfillment. In the game, the fate of Supideo's birth parents with respect to the original prophecy is reversed, in that Kassandra has the option of sleeping with Kosta and kills the bandit leader.