In 1999, Grams tried to warn her granddaughters of a coming evil by opening the Book of Shadows on an entry called "Rite of Passage". Phoebe began to read the entry, but couldn't finish as Abraxas attacked and took the book into the Astral Plane.
From the small piece that Phoebe could read, the entry said that the sisters could fight Abraxas with the Power of One. Piper thought that the entry meant that Prue could defeat Abraxas, as she was the first born sister with the strongest power. Prue, who was till grieving Andy Trudeau at the time, struggled with this responsibility, though her sisters eventually learned that it was not Prue, but all three of them that form the Power of One by working as one.
In 2009, Phoebe Halliwell used a variation of the spell Dominus Trinus to tap into the Power of One again. She was able to communicate telepathically with Piper and Paige, even though each sister was in a separate dimension.
- Hear now the words of the witches,
- The secrets we hid in the night.
- The oldest of gods are invoked here,
- The great work of magic is sought.
- In this night and in this hour,
- We call upon the ancient power.
- In the episode "The Wendigo", Piper called herself the Power of One while alone in Golden Gate Park facing a phone booth.
- Paige makes a similar reference in the episode "Witch Wars".