The Source

 "The Source, after many failures, decides to destroy the Halliwell sisters himself. He devises a final plan to unleash The Hollow – an ancient force that can absorb all magic, both good and evil. His plan is to use The Hollow to take the sisters' powers.

However, The Seer, a high-ranking demon, has her own plans. She betrays The Source and meets with the Halliwell sisters. She offers them a dangerous deal: use an ancient spell to absorb The Hollow themselves. This will give them unparalleled power, enough to destroy The Source once and for all.

The problem is, The Hollow's power is too great and can destroy anyone who uses it. In addition, Phoebe has a terrifying premonition that if they follow through with this plan, one of them will die."