From A Brief Primer for the Modern Mage, authors including (the list spills on for some time)
----------------------------------------
The soul is at the heart of all magic. It is what connects the body and the mind to the ethereal, what enables thought and action to push against the elements and enforce change upon reality. Accordingly, a basic understanding of it is essential for any mage to understand not only how they cast the spells they do but also why some magical disciplines are simply incompatible.
----------------------------------------
To think of the soul being like the body is a fundamental misunderstanding, as each ‘part’ of the soul is not some distinct portion of the soul, but rather a function which the same fundamental object takes. This can be seen in how a piece of the soul may be partitioned off in any manner chosen, and the budded soul is able to be fully self-sufficient upon its own, even becoming a separate entity from the originating soul in time, developing any portions of the soul which the donating being may have lacked, such as a fragment of a tree’s soul developing a Mind if placed within a sentient but soulless creature. In addition, a single fragment of Aura may be studied to learn of the Akash or Icon, and may be utilized to draw from the Reserve.
Yet at the same time, the soul undeniably does have a shape, an exterior and an interior. It is impossible to access the Anima without first piercing the Abla, and the Reserve undoubtedly passes through the Shape before it leaves the soul.
The soul is the exact shape of the person, yet it is also an iconography unique to that individual. It is a perfect sphere nestled within the body and a diffuse presence filling the surroundings of a person simultaneously. Souls are composed of quintessence, the same stuff which the Divine realms are formed from. The religious connotations of this besides, it is important to understand that souls do not operate by the normal physical laws. However, as this is intended to be an introduction to the soul’s functions, we shall take it as a given that the soul does what it does and not prove its various aspects. The diligent student may be interested in the mathematical analyses of the soul’s properties which advanced necromancy textbooks may provide, should they desire to learn more.
----------------------------------------
The souls of most living beings are predominantly Radiance-aligned, with all the wild and insurmountable nature which accompanies that particular element, but some souls may utilize any of the other Foundational Elements instead. This is what distinguishes an Elemental from other types of beings, with the exception of Shadow-aligned souls, which is the domain of undead creatures (and is the reason which Radiance and Shadow are occasionally referred to as the Life and Death elements). While each of these have their own fascinating behaviors, for the purposes of this introductory lesson we shall proceed with the assumption that the studied soul is the Radiance-aligned soul of a sentient mortal creature.
There are roughly three sections to the soul: The Aura, the Mantle, and the Core.
----------------------------------------
Aura
The Aura is the outermost part of the soul, comprised of the Abla and Mind. This portion of the soul is dedicated to interaction and protection, interfacing with the world around it to defend the soul. This is often done by pushing potentially damaging magics and energies to the physical body, and is why non-physical attacks, such as pure Shadow, physically harm their target. It may be useful to conceptualize this reaction as akin to a fever, an automatic protective response which can nonetheless cause great harm to the individual. Furthermore, this mechanism can of course be overwhelmed, and leads to soul damage. Furthermore, the Aura is the only part of the soul which can be consciously controlled by the individual.
This is most obvious with the Abla, as many magical disciplines utilize proficiency in utilizing it to directly cast magic, stabilize the local Manic field for their own spells, or overriding the Manic field with their Mind and/or Icon, among countless other uses. Nearly every spellcasting tradition utilizes the Abla in some way, but for my example I shall reference Psionics, which manifests the aura physically, either as a force or non-mana energy construct.
The other part of the Aura is the Mind, which is the manner by which the soul connects and perceives the world around it. Magical senses nearly all rely upon the Mind in some form, and some magical disciplines utilize the Mind to directly override portions of reality with their own will. The Mind likewise is the portion of the soul which holds all of the individual’s memories and thoughts, directly interacting with the brain (if they possess one) as one of the two intermediaries between body and soul. Likewise, the Mind is the most prone to observation or detection by other magical senses. When viewed with a soul sight spell, it is the Mind that is responsible for the behaviors and characteristics (usually manifesting in colors and patterns) which make it possible to determine emotion, though that can be obscured by the Abla with sufficient practice. Similarly, it is the Mind which Mentalism most interacts with, both when the caster is attempting to overpower the will of the world and as the target for when they attempt to control a living being.
----------------------------------------
Mantle
The Mantle is the middle layer of the soul, and is where the Shape, Reserve, and Icon all reside.
Of all three, the Reserve is the simplest to explain, as it is the portion of the soul which holds and produces magic. The exact mechanism by which the soul creates mana is under continuous debate, given how closely tied it is to the debate for the origin of magic itself, and suffice to say that each Grand Theory of Magic possesses their own explanation for the mechanism by which the soul produces mana (some assign this role to the Anima). Investigation into that topic is left as an exercise to the diligent student.
Unauthorized reproduction: this story has been taken without approval. Report sightings.
Regardless of the method by which it gains mana, the Reserve is the most reliable method of storing magical energy ever found, discounting a few Divine Artifacts. Mana within it functionally never leaks out unless the Reserve is seriously damaged, or when it naturally releases mana beyond its capacity to contain. It can be extracted from, naturally, but doing so utilizes a different method than what occurs when mana passes through the ‘membrane’ which the Reserve functions as.
While most classical magical disciplines rely heavily upon the Reserve, it is Enhancement which most explores its potential. It pushes the mana contained within the Reserve to the rest of the soul and body, empowering both directly instead of attempting to direct it out through the Shape and into the surroundings.
The Icon can in some ways be best summarized as the ‘fingerprint’ of the soul. This is not directly connected to the actions of the individual, but is rarely wholly divorced either. It serves as a semi-abstract summary of the person’s soul in its entirety, yet in a manner disconnected from their Mind and Akash. It is, in some ways, the ‘inner self’ of the person, and reflects their true intentions and inner drive, modified by any corrupting influences upon them. Enchantments which divine if a given person is ‘worthy’ often rely upon the Icon, if they do not commune with a god or other divine being.
Furthermore, it uniquely impacts the mana of the person, and is widely believed to be the source of mana signatures. It is also one of the two parts of the soul occasionally known as the True Name, and is the more commonly used of the two. Unlike the Ren, the Icon’s True Name can and does change over time in response to experiences underwent by the soul.
In some cases, it can interact with the Shape in unusual ways to grant talents unique to the soul. Some Bloodlines reside within the Icon in some form or another, and it serves a foundational role in Essentialism, as it is the basic source from which the user’s Will is imposed upon reality.
The Shape is the portion of the soul most often responsible for innate magics. It acts as a sort of spiritual muscle and sculpture simultaneously, and with its position right along the edge of the Reserve, has the most direct access to mana of the entire soul. It is also the easiest part of the soul to actually change (the Aura does not fundamentally change, it is simply controlled), and simple practice will leave an indelible mark upon it. Shaping relies upon this fact, attempting to build up the Shape’s capabilities with minor magical abilities, blossoming from a basic Spark spell into all manner of non-spell magical capabilities that may be called upon with no more difficulty than moving an arm.
In addition, many disciplines seek to artificially impose some change upon the Shape.
Crystalurgy is the most prominent form of these artificial changes. When a crystal is absorbed, it imprints a specific magical formula upon the Shape, functionally enchanting it as though it were an artifact and forevermore giving the Shape a method by which it can influence the world around it. Thanks to the flexible nature of the Shape, these abilities can be grown through simple practice, but can only rarely be changed fundamentally once set. It is, simply, easier to add to the Shape than to take from it.
----------------------------------------
Core
The Core of the soul, consisting of the Akash, Ren, and Anima, is where the most foundational portions of the soul are located, and as the deepest part of the soul is the most difficult to observe and interact with. There exists some belief that a sum total of all that a being has undergone and accomplished is stored within the soul, in some portion of the soul. Some assign this property to the Ren or Akash, but neither properly possess the correct capabilities. The current leading theory is that there exists an undiscovered portion of the Core known as the Records which documents this, but its existence remains purely theoretical.
The Akash is the part of the soul which matches to the body, and acts as the template which automated healing spells, including divine spells, are based from. This is the part of the soul which keeps the metaphysical anchored to the body itself by serving as an excellent match to the body. Shapeshifters who possess multiple ‘true’ forms, such as werewolves, may possess multiple Akash, one for each of their forms, which informs their bodies as to the correct states wherein they may exist in relative stability.
Over time, the Akash shifts in accordance with the body, as beings grow older, and Magimorphosis is the result of extreme exposure to mana (usually from the Icon and Shape) influencing the Akash in their own way.
Natural fleshcrafters, including elves, have a far more mutable Akash than typical, enabling them to have their shapeshifted forms function as their ‘true’ forms for those spells which care about such things. Biomancy, naturally, interacts heavily with the Akash, as practitioners of Biomantic disciplines seek to remake their bodies to be naturally magical, and to do so in any true factor necessitates alterations.
The Ren is the other of the two things sometimes known as a True Name. Unlike the Icon, however, the Ren is wholly static. The True Name which it imparts is formed alongside the soul and does not change for the entirety of the soul’s existence. There is no proof that the Ren has any bearing or relation to the personality or capabilities of the individual bearing it, and certainly has no influence over personality. It is, however, completely unique with an infinite number of possible expressions, as proven by Elstat’s Theorem and Torvil’s Proof. No two souls are capable of possessing identical Ren, and thus if two Ren are identical, they originate from the same soul.
Binders naturally utilize the Ren frequently, utilizing the knowledge that comes with knowing a soul’s Ren to bypass many of the soul’s defenses. However, it is Inheritamancy which bears a particular mention here, as it is the only discipline of magic which actually seeks to utilize a Ren as an aid rather than a method of control. This is accomplished by bestowing a powerful bloodline onto one of the parents, often overriding virtually all else about them beyond the power of the Bloodline. This occasionally results in the child possessing the Bloodline as a part of their Ren, granting them a potent magical ability which possesses essentially none of the normal drawbacks which come with such and has a far higher likelihood of being passed on.
Lastly, the Anima serves as the very core of the soul, a power source and basic structure of the rest of the spirit. It is the Anima which the rest of the soul is built upon, and is completely impossible to destroy, though its indestructibility has not yet been proven.
It serves as the power source for the rest of the soul, enabling it to continuously function, and either directly or indirectly fuels the production of mana. Regardless, the healthier and more powerful the Anima, the stronger the surrounding core and being is. It is this very fact which makes dragons so potent, as their Anima (unlike most living creatures, dragons never stop growing their Anima, which grants them strength beyond belief). Similarly, Cultivators seek to grow their Anima, making themselves and their souls substantially stronger and healthier. However, influencing the Anima is exceptionally challenging.