The Soul

Souls are more or less big knots that develop out of Emotions, and that are stabilized in a physical body. This invisible part of Magic not only contains all the feelings of a living being, but in general its character, aspiration, and memories.

Living beings

The Soul constitutes the spiritual or mental part of a creature, its spirit, character, personality or its psyche. Without a Soul, the body is a literal empty shell. Through a Soul the body is capable of moving, or at least to influence its environment in one way or another.
Moreover, the Soul provides the body with an Aura as well as the ability to do Mysticism.

Properties

Souls with a body:
A being is confronted with a lot of feelings, experiences, dreams and ideas during its life. The Soul, which is stabilized inside the body, will grow this way. That is how a creature's character is developing further and further or even may change during the course of a lifetime.
Souls without a body:
Souls that loose their body are very unstable and will dissolve over time. These Disembodied Souls may turn into a serious threat to their surroundings.

At first glance:
The Souls is spiritual Magic knotted together. It provides personality, aspirations, and mystical abilities. Souls without a body will dissolve over time.