Heartless

Heartless magic is the process of possessing others for their own gain. There are many names for the practitioners who use this form of magic; Liches, Hags, Parasites, etc.<ref>Heartless
Heartless give up their body. The inverse of the Host, they work to make themselves the possessing force. They are the liches, the hags, the parasite forces, and more, often losing the ability to practice over time or over generations as they leave their human origins further and further behind. - Pact Dice: The Practices - Wbow Version</ref>

Methodology

Heartless is a immaterial and price oriented school. Every use gradually pushes the practitioner away from humanity and closer to becoming Other. However it is an excellent way to quickly regain power, youth, and other abilities. They tend to focus on the long term. Often preferring to stick to small, subtle effects, and then constantly layering it for reinforcement.

Notable Heartless

Crone Mara
Mags - may count in some sense.

Trivia

The title of this school recalls the russia mythological figure Koschei more commonly called Koschei the Deathless. His soul being hid within a convoluted series of objects is commonly cited as the inspiration for liches.
Probably unrelated to the dark folks in kingdom hearts.

References