Witch

A witch is an immortal being that is born from a specific human emotion or earthly desire.

Origins
A witch is born from a specific human emotion or earthly desire. For example, Suri is born from the human desire for vengeance, therefore she would hear the soli and collect the energy that comes from human moments that feature a desire for revenge. Witches have no memories of how they came to be, only that their mission is to hear soli and collect energy to maintain themselves.

Characteristics and Abilities
All witches are female.

Witch's Core / Marble
Witches are born with an external core that takes the form of a marble or an item of jewelry. This item maintains a witch's immortality and is otherwise the source of her power. Other witches or demons find it easy to steal and absorb a core and often do so to increase their own magic, but witches will not die if their core is destroyed or placed far away; the witch and her body will simply no longer heal supernaturally and she becomes susceptible to mortal danger. The witch must keep her core close in order to practice her supernatural abilities.

Hearing soli aka 'Sound'
All witches are born with the ability to hear soli (literal: sound), which express the witch's uniquely-assigned desire or emotion. Witches hear all instances of such sound no matter the distance and will track the specific location of certain sources in order to feed on t he energy of such emotion and events. This is how a witch 'makes their living'. Mei believes this process of answering and quieting soli is the source of earthly order and the lack of this process results in earthly chaos.

Special Ability
In addition to soli, each witch has their own unique super ability, varying from self-duplication to mind-reading.

Demons
Witches have the ability to create beings called demons. Demons require constant infusion of the witch's power so they are often difficult to maintain and therefore made only by higher level witches.

Demons usually start with the souls of animals that are at the brink of death and their life-energy is about to scatter. When a witch casts her magic on the chosen animal, the animal's life-force is contained within a new spiritual bowl, or container, which results in an unwritten contract and the demon having a human form. If the witch fails to feed her magic to the demon and sustain her custom-made spiritual container, the demon will revert to a ghastly form of the original animal and succumb to a slow and painful death.

Theoretically, the demon can be a useful and loyal companion. In reality, demons often betray their contract witches in one form or another and are the leading cause of witches' death. The most notable example of this is the main plot of Witch Hunt, Suri's death.