Medea
Medea, a sorceress, had become Aegeus's wife. Medea was scared that she would lose her influence over Aegeus if he found out that the the traveler was his son, so he convinced him to give Theseus a cup of poison. However, at the last second, Aegeus recognized Theseus's sword and stopped him from drinking it. Medea fled to Asia after she was revealed.