Souls are of significant importance in Baltia, as they are the root of all energy within the world. Souls are the primary source of magical energy in the world of Baltia, with the oldest and most prominent forms of magic using the energy released by souls as the fuel to create miraculous effects. As a general rule, all mortal creatures that are “naturally” born into the world will have a soul, including even plants and insects. However, not all souls are equal.
Even the smallest blade of grass technically has a soul. However, its soul is so small and weak as to be functionally imperceptible unless one looks closely. Similarly, the soul of this blade of grass puts out nearly no energy at all - but it does indeed put out the tiniest bit. This little bit of energy, when multiplied against the countless blades of grass that exist in the world, begins to add up over time.
Further, the more complex a creature is, the more powerful its soul and the more energy that soul puts out. A tree's soul is more powerful than the soul of a blade of grass, the soul of an animal is stronger still, and the soul of a humanoid even more powerful still. When examining the beings that naturally reside in the mortal world, those creatures that tend to rest at the top when it comes to soul power are those one would likely expect - dragons, krakens, and other creatures that are singularly considered extremely powerful.
Souls seem to, for lack of a better term, simply spring up. The exact mechanism behind their creation is a mystery even to the gods, or at very least, the gods claim this to be the case. In any case, it seems unlikely that the gods are responsible for the creation of souls - the Old Gods were once mortals, and as such, most certainly have souls of their own. The New Gods, meanwhile, emerged well after souls were an identified phenomenon. Where, then, did souls come from?
The leading theory among mortal scholars is that souls are not created intentionally, but are simply the result of interactions between the membrane of Baltia and the realm of the Outside that surrounds it. These scholars, and the textbooks they write, theorize that souls materialize within the Outside. Should a soul that is materialized within the Outside be close enough to the membrane of the world (as much as the concept of distance can matter in the Outside) then it has a chance to filter into Baltia.
It's speculated that only the smallest and weakest of souls, like those of plants, could filter through this membrane. However, once they've done so, these souls find themselves within the realm of the Afterlife.
Those who have come back from death claim that the afterlife is a world much like our own, so much so that some even struggled to recognize that they had died due to the similarities. There are communities, plants, animals, and anything else that one has come to expect from the world of mortals. But these surroundings are not believed to be mere decorations - they too are likely transient beings in the afterlife. When one sees a tree in this realm, they are in fact seeing the soul of a tree. When one sees a man, they are seeing the soul of a man.
It's unclear whether this is some form of deliberate effect, where the gods have willed souls to take on the forms of their most recent incarnations, or if souls are simply perceived to be in the same forms they inhabited in life. It could indeed be that in the afterlife, we simply see the souls that surround us in a form that has become logical and comfortable to us over the process of living in the world of mortals.
With the exceptions of celestial and fiendish beings, all souls in the afterlife are likely to be reincarnated. For humanoids, this is typically a challenging processes - one is not able to begin a new life without active effort. For most, this effort means finding their way to the nearest servant of a god capable of releasing them back into the mortal plane, though some allege that there are other means to enter the next life.
However, plants and animals lack the intelligence to actively seek out such a fate. Do they reincarnate, and if so, how? Once again, the gods are either unwilling or unable to provide conclusive or meaningful answers to these questions.
There are a number of theories on the subject. The most popular one is that the less powerful a soul, the easier it can “naturally” move into the world of mortals overtime. Therefore, plants may simply reincarnate after a short period of time, while the same may occur for animals after a longer one. Proponents of this theory often believe that the gods deliberately prevent self-aware creatures from reincarnating in this same way, so that they can identify potentially useful mortals before sending them to their next life, or in order to prevent fiends from being incarnated into mortal flesh.
Regardless of the specifics of how reincarnation works, the processes is extremely important for souls, as it is what allows them to grow in power over time. As a soul lives within a mortal vessel, it gains new experiences that are necessary for its development. Then, once its current mortal form has expired, the soul is freed from its shell and able to grow. The process is remarkably similar to the practices of the hermit crab, migrating to larger shells as it ages and grows.
Once a soul is able to be reincarnated, it will be bound to the next available vessel that is capable of holding this soul. The mortal form of a sapling is completely unable to hold the soul of a human being, and so that human will never be reincarnated as a plant under normal circumstances. However, some souls are more flexible than others - it's not uncommon for some beings to have many lives as different races, while another soul may only ever find itself contained in the flesh of beings that have much in common.
In the earliest days of its existence, a soul will take on a series of mortal vessels. These vessels will each grant it the ability to experience the world, to improve, and to grow. Then, in death, the soul will theoretically have the opportunity to reincarnate into a more capable being that will be able to experience even more. Souls that experience the full gauntlet of forms may find themselves beginning as small and short-lived plants before moving onto larger ones, then being incarnated as simple animals like insects, before then taking the form of animals and eventually humanoids. Humanoids may eventually find themselves being born as something even greater, in time, such as a dragon.
However, reincarnation is not a process lacking in danger. While it is difficult (but not impossible) for a soul to be harmed while inhabiting a body, the soul is quite vulnerable in the afterlife where it has no such protective vessel. The greatest threat posed to a soul in the afterlife is the threat of Fiends. These aberrant souls have forsaken normal growth in favor of destructive shortcuts.
The most common and most tragic type of Fiend is the demon, which is formed by the coagulation of many souls into one identity. This is almost always accidental, typically as a result of several weak souls being simultaneously pushed to their limits. It is best compared to the mob mentality that one can witness in a crowd of mortal beings, and it often emerges under similar circumstances. For example, should a group of humanoids find themselves being hunted in the afterlife in the same physical area, the shared location and shared emotions may cause their senses of self to blend together.
When this occurs, a demon is born. In the afterlife, their forms combine into one being that is often the physical manifestation of their most based instincts or fears. Most demons take on gruesome or terrifying forms as a result. However, the collective energy of these multiple souls grants the demon greater power to protect itself, and the demon will often seek to grow further so it can increase this power. They then often go on to hunt isolated souls that they can add to themselves, or even lesser demons should they find any.
A demon remains unique in that it is still technically a collection of beings - while it shares a single physical form, it technically can have a multitude of identities. However, one is unlikely to see strong influence from any single soul, as the whole is far more powerful than any single member. As a result, its actions tend to adhere to the “lowest common denominator” so to speak, resulting in simple motives and expressions.
Much like demons, Devils are fiends which hunt for the souls of the weak in order to strengthen themselves without going through the process of reincarnation. However, unlike demons, devils maintain a singular soul and identity. They do so by combining their souls with those of weaker beings, fusing the two souls together into a singular more powerful entity. This allows them to maintain a sense of self that demons lack, while still absorbing the majority of the power of the “victim” soul.
However, this process is not without its drawbacks. All souls have traits and personalities, and when one soul absorbs another, their traits are combined. This results in a personality shift within the devil, the magnitude of which depends upon the relative power of the two souls. A devil which has consumed a soul close in power to its own may change radically, while a devil harvesting weaker souls may change little from meal to meal.
Even if the change is small, a change has occurred. Traits that the devil share's with its victim soul are magnified, while any traits the devil has that are contrary to those of its victim are diminished. If a devil favors a certain type of prey, the result will often be personality traits that are taken to sometimes comical extremes. Even if they do not have any preferred type of victim soul, there are some traits that simply make one type of soul easier to hunt than another.
The last major category of fiend is the yugoloth, which is considered to be the most depraved and vile of the fiends. Unlike devils, which preserve some manner of their victim in themselves, yugoloths show no such mercy or respect. They simple consume the souls of their victims, shredding them into scraps of energy that their own soul then consumes. This process means they do not see personality changes in the same way that the other fiends do, but is far less efficient - a yugoloth only grows by a fraction of the consumed soul's overall power. This lessened growth is worth it to them, though, in exchange for remaining their true selves.
Unfortunately, the true self of such a being often leaves much to be desired. There is much to be said about a being who believes itself entitled to destroy the souls of other sentient beings to fuel itself, and little of it is pleasant. Such beings tend to value their own existence above all others, and even further, often value their wants or fancies above others as well.
Once a mortal soul has been reincarnated enough, it may become sufficiently powerful to enter the service of a god. When a soul finds a god it wishes to serve, and the god accepts its service, that soul will become known as an angel. It will no longer be reincarnated under normal circumstances, and will instead remain in the afterlife alongside its god. Angels act in whatever role is needed of it, typically acting as a soldier or administrator.
Angels are further enhanced through access to a fragment of their god's power, which they can call upon should their own power be insufficient. While the soul itself will no longer grow after becoming an angel, a god may promote its servants by giving them greater access to its own pool of power.
All souls create energy at a constant rate, with the amount of energy created by a soul being one measure of a soul's overall power. The second measure is the amount of energy a soul can store at a single time, with the more powerful souls being capable of holding a greater amount of energy. These two measures tend to be strongly correlated, though there are cases where a soul is strong in one aspect and weak in the other.
The amount of energy a soul can produce is theoretically limitless - so long as a soul exists, it will be capable of producing energy. However, every soul has a maximum amount of energy that it can hold at a single time. Once it reaches this limit, and can hold no further energy, any new energy it creates overflows into the world around it. This is the root source of ambient magical energy.
This energy remains in the world until it transforms in some capacity. There are many creatures in the world that are able to harness ambient magic, such as plants that have evolved to no longer need the sun. This energy is most notably used by individuals such as Wizards and Druids, however, who use it as the fuel for their spells.