Spirit

Entity
When a creature possesses a high level of anima, its Core may contain a Spirit. Spirits are potentially found in all forms of Creature Cores, though typically, it is exceedingly rare amongst lower order Magical Creatures. For Spirit-Seekers, the irony lies in that billions of low-tier creatures exist with a lottery's chance of possessing a Spirit. While beings with a high probability of retaining a Core upon death, as well as possessing both ego and anima, are exceedingly rare, and more often than not incredibly powerful.

Spellcraft
A Mage dreams of augmenting their elemental powers with a Spirit. A Spirit may be acquired through directly killing and harvesting Cores, then bending the will of the 'anima' of the creature contained therein to the Mage's service. When successfully attuned, the Spirit is absorbed into the Mage's Astral Body, becoming a part of the Mage's ability to channel Elemental powers. The alternate method of gaining a Spirit is through taming existing Magical Creatures and opening one's Astral Body to the foreign Spirit. This methodology is considered highly irregular and potentially fatal for an unsuspecting Mage incapable of melding with the entity.