The demonic power stripping ritual is a ritual used to strip a demon of their powers, even their immortality. However, it is presumed that this ritual does not have the ability to strip witchly and other magical powers. It requires the caster to slice their palm with a specific dagger, and for the one whose powers are to be stripped to subjugate themselves by kneeling before the caster. Unlike other rituals or spells, there doesn't seem to have a required incantation or it can be cast nonverbally.
At some point after leaving to find himself in "The Source Awakens", Parker Caine came into possession of the dagger required to perform this ritual. He attempted to use the ritual in "Past is Present" to strip his half-sister, Abigael Jameson-Caine, of her demonic powers, but she was able to retain them due to having eaten an apple from the hallowed tree in Sacred Grove.
In "Needs to Know", Abigael is approached by Macy Vaughn who wants help in removing her demonic powers - in hopes that this will aid in restoring the Power of Three. She escorts Macy down to the dungeon, revealing that Parker is alive as he is the only being that knows where the ritual dagger is that is needed. Abigael threatens Parker, even telekinetically flinging him up against the ceiling of his cell, before Macy says that she will speak with him.
After having obtained the knife, Abigael performs the demonic ritual to strip Macy of her demon powers. She later returns to the dungeon, showing Parker that she had not only stripped Macy of her demonic powers but that she had stolen them for herself.