Theodorus was a soldier in Xena's army when the Warrior Princess was attacking Arcadia. He was in love with Xena and she used his love. Xena sent Theodorus on a suicide mission to kill Hercules because she knew that once Hercules had defeated him, the hero would come looking for her and Iolaus. Indeed, that is exactly what happened. Theodorus planned a sneak attack on Hercules in Alcmene's barn and Hercules killed him in self-defense.
Theodorus's relationship with Xena led some early commentators, such as James van Hise in his Hercules & Xena: the Unofficial Companion to suggest that Xena ensured her troops' loyalty through sexual favors, but her manipulation of Theodorus is the only real example of this, though she had no trouble using sex as a weapon if needed.