Spirit

Not much is truly known about the Spirit, other than that it is the crux of spell-casting. They have fairly tangible forms, however they are unseen by most. Most have fairly faint spirits, but some can have a larger presence than others which helps in casting powerful magic or crafting legendary artifacts.
One can live a normal life without a spirit, however they forfeit the ability to use magic altogether and it becomes much harder for them to defend themselves against malignant spells. Being spiritless can also make healing less effective, making it harder for them to be treated if they are badly injured or have been afflicted with a disease.
It is theorized that spirits can be taken and used, however that knowledge is only privy to the most powerful and amoral sorcerers.

Manifestation

Often characterized as a light blue, transparent glow that hangs behind the person in question.

Type

Metaphysical, Arcane