~TERMINOLOGY~ Mana and The Essence

Mana is the source in which magic and psionic energy are both respectively drawn from, a source that is connected to the psyche and the heart. It is a force of neutral energy that is produced by the soul.

                                                                                                    Mana

Within the heart dwells Essence, or life force, a vital component to the use of magic. Also known as Spiritus, all living things are known to have Essence/an Essence. When an Essence is strong enough to bond with its dormant mana, the body is then able to create magic.

On the other end of the spectrum, there is the bonding between the psyche and mana which occurs when the limits and boundaries of the psyche are loosened enough to willingly draw mana from their souls at will. In turn, this allows the psyche to create psionic energy.. 

                                                                                            The Essence

Magic, Exchange, and Signatures:

 Magic is a force that requires and exchange in order for its power to be accessed. Those who possess magic when powerful enough are able to simply exchange their mana for the power to cast spells, mana being a source that's able to be replenished unless there is something that prevents it from doing so (damage to the soul, diminishing life force, etc.). The exchange is able to be carried out in a number of ways, whether that be by exchanging the hairs on the users head one by one, a possession that belongs to the user, sacrifice, or the easiest method for the much less experienced or those who have smaller life forces but are still able to produce mana, by use of blood. 

Signatures allow magic users to tame an object in the sense that allows them to bend and transform the object at will, extending a greater sense of ownership onto the object in question. Magic signatures are extensions of an individuals mana, and so this is what allows them to place ownership and authority over what their signature is placed upon. Inanimate objects are the easiest to place signatures upon since they lack a will of their own. 
In the case of living beings, a user of magic with a powerful enough Essence is able to overthrow the signatures of those with weaker ones and rewrite them altogether. It is also possible for the more skilled magicians to dispel signatures. 

        Natura  

Natura is nature, yes, but it is also birth, as is it qualities. Natura is the nature, or qualities of an individual's magic.

• Yasha's example for Yoon: "For instance, the birth of your magic was when it bloomed. The nature of your magic is that you are an elemental of the winter, and thus your magic bares the qualities of one of the three natura cycles of that it consists of. The Cycle of Tears, the Cycle of Haze, and The Cycle of Frost, these are the three cycles of winter. Your natura bloomed in the Cycle of Frost. Your natura is where the core of your abilities are built upon if done so properly." 

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Natura is the nature, or qualities of the users magic. The birth of an individual's magic would be their blooming. The nature of their magic is that you are an elemental of the winter, and thus your magic bares the qualities of one of the three natura cycles of that it consists of. The Cycle of Tears, the Cycle of Haze, and The Cycle of Frost, these are the three cycles of winter. Your natura bloomed in the Cycle of Frost. Your natura is where the core of your abilities are built upon if done so properly