The Source's Heir was the unborn son of Cole Turner and Phoebe Halliwell. He was a half-demon whose conception and birth had been planned and manipulated by the Seer. The union between Cole, who was possessed by the Source of All Evil, and Phoebe, a Charmed One and former Queen of the Underworld, created a tremendous concentration of power. Even as a two-month-old fetus, he was able to perform terrible yet nonetheless spectacular feats of magic through his mother. Against this power, even demons thought impossible to be vanquished, perished.