The first of the four abilities spheres is linked to the first of the Three Great Forces, as well. That said, I confess that despite studying psionic abilities and their functions for many years, I still do not quite understand how they work. In the end, it matters little - the significance of these abilities is in their versatility and invisibility; unlike Elemental or Magical abilities, one can never be sure when a psionics are in use.
— "Power: A Treatise on the Existence and Interaction of the Four Systems" by Oriana Tansea
 

The Nature of Psionics

Much like Elemental Affinity and Magic, Psionic abilities are based around the manipulation and production of one of the three great forces present in Empirica Sin. In this case, one creates external and internal effects by shaping, generating, and channeling energy within one's own body - the energy called Od.

Psionic Spheres.

Self-Affecting

Extra-Sensory

All abilities related to senses and perception. Some examples are clairvoyance, prophetic visions, the ability to read and analyze energy.
Notable Users: Leviael Kythien, Grigorius Bieloskytes, Eiryen Nesaleen

Metabolisis

The ability to change or affect one's own body. This includes things like enhancing one's own physical power or increasing the rate of healing. It also includes more complicated abilities like shapeshifting.
Notable Users: Leviael Kythien, Dagon, Grigorius Bieloskytes

 

Other-Affecting

Communication

Abilties that involve the user's mind or spirit interacting with the mind or spirit of someone else. This includes other sapient creatures as well as things like animal communication. It also includes dream-walking.
Notable Users: Eiryen Nesaleen

Extra-Metabolisis

These abilities affect the bodies of others. It is the outward facing equivalent of Metabolisis and can be used to heal others, for example, or to enhance their own abilities.
Notable Users: Dagon

External Od Manipulation

The abiliity to affect the Od of others. This is most commonly used to stop an action or attack, for example severing a pyrokinetic's control over a fire. However, at the highest levels this becomes more complicated and versatile and can permit others to trigger a psion's abilities, essentially controlling the abilities of someone else.
Notable Users: Leviael Kythien

 

World-Affecting

Creation

Creation abilities are related to using one's will and od to create external constructs. They can be physical, such as forming a sword or force field from odic energy, or intangible - for example generating light, sounds or illusions.
Notable Users: Dagon

Psychokinesis

A powerful sphere that allows the manipulation of various things - pyrokinesis controls fire, telekinesis allows the movement of objects, etc.
Notable Users: Grigorius Bieloskytes, Dagon

Meta-affecting

Destruction

Destruction is a discipline aimed at taking generally benign psionic abilities and altering their functions into a more offensive/destructive direction. Telepathy might become psychic attacks or mind control, and extra-metabolisis might allow a user to make the target's body begin to consume itself at a rapid pace. Note that some abilities already have an offensive applications (e.g. forming a sword or enhancing a soldier to fight for the user), but Destruction permits a more direct application.
Notable Users: Grigorius Bieloskytes, Leviael Kythien, Dagon

Essential Information

Prevalence by Species

 
Ability Celestials Mortals Demons Comments
Palen 5% 50% 45% No ability to manipulate, or inaccessible ability. This is extremely rare among Celestials.
Enop 20% 25% 25% A low level of ability capable of small/simple manifestations. It is fairly common for a Celstial to have this level of ability, particularly the weaker fae and young aurali. The most common level for Mortals and Demons with Odic abilities.
Modu 40% 15% 20% The most common level of ability for those who have the ability to begin with. Capable of small but more complicated tasks or larger but simple tasks (e.g. lighting a furnace). This is the level of an average fae or Aurali.
Dumen 20% 5% 7% The level of ability demonstrated by particularly gifted or experienced Celestials such as veteran soldiers.
Vaham 10% 3% 2% The highest rank (naturally) achievable by most non-Dei Celestials without Ascension or promotion. It is also the lowest rank for Dei under normal circumstances, and the typical level for an Aurali Serat. This level is nigh unachievable for Demons without Exedis, or by mortals. Larger and more complicated abilities are available.
Vallus 4% 2% 1% This is the level of ability typical to the most powerful Aurali Serata, high level Deivas and low level Deities. It is also the hard ceiling for the natural ability of Demons and Mortals; Exedis can still bypass those limits. Mortals have not as of now achieved the ability to bypass this limit
Vis 1% 0%* 0%** The level of ability common to strong Deities. There are no mortals at or above this level of ability in psionics; there are statistically zero demons, though a few outliers do exist.

*Literally zero. **Statistically 0, not 0 in hard numbers.

A Note about the Nature of Ranks

Due to the nature of psionics, a person's ability can vary greatly based on mindset or situation. Generally, their average level of ability is considered, but it is always best to bear in mind that stress may impede ability just as determination may enhance it.

 

A Note about the Nature of Spheres

Unlike the more instinctive Elemental Affinity Sphere or the more chaotic Magic Sphere, Psionic power is strongly reliant on the ability of the user to focus and shape, a process which requires some level of self-discipline.

That said, for Celestials (and even Demons to a lesser degree) this is a somewhat natural process without obvious demarcations between abilities. For Mortals, however, organization and categorization helps to break down the process of accessing abilities and facilitates more efficient use.

Essentially, the Spheres and systems above were designed by Mortals; these are being used for ease of understanding and reference. However, a Celestial would never consider themselves to be, for example, a Metabolisis Psion, because they do not think in demarcated spheres. To them they are simply using their natural abilities which can differ from person to person.

All of that being the case, it should be understood that having access to one ability inside a specific sphere does not necessarily imply ability in everything that sphere can do, much less equal access to all abilities. In other words, having prophetic visions does not imply the ability to analyze energy despite both being filed (by Mortals) under the same Sphere.

 

Celestials and Psionics

As mentioned above and elsewhere, psionic abilities come very naturally to Celestials, with the vast majority possessing at least some odic abilities. Celestials also generate significantly more internal energy than, for example, mortals... and as such, they do not need to be quite so careful in wielding their abilities. That said, there are limits and Celestials can and have burned through abilities too quickly and damaged or killed themselves as a result.

Because of the nature of Celestials' relationship with Od and psionics, their specific connection of abilities can be wildly scattered - a sensory ability here, a psychokinetic ability there, topped off with a seemingly random extra-metabolic ability. In other words, their power sets are very individual to themselves and often reliant on their personalities and personal alignment with elements or interests. Their natural level of ability is also considerably higher on average than that of Mortal or Demonic users.

Demons and Psionics

Demons also generate significant levels of Od, however their personalities tend toward the chaotic (perhaps as a result of their use of Void Energy), making it difficult for them to master these abilities. That said, psionic abilities are, while less common among demons than Celestials, still relatively common at low levels. However, as ability ranks rise, the percentage of Demons operating at that level falls off before hitting a hard ceiling at Vallus. In order to move beyond that cap, a demon must engage in Exedis and expand their potential.

Natural psionic talents can be just as scattered as Celestials, but generally with far fewer specific abilities. However, Demons who developed psionic powers consciously through practice will tend to have abilities that are more concentrated in a specific area.

Mortals and Psionics

Mortals, by their nature, are more flexible than both Celestials and Demons, and as such they are capable of achieving high levels of ability in psionics with neither the ease of the Celestials nor the struggle of the Demons . That said, there are some obstacles to mortal mastery of Odic powers - primary among them the comparatively low speed at which their body replenishes burned Od. Furthermore, because Mortals do not have a natural inclination toward psionics, they have had to invent a training regimen to discipline their minds and bodies to access their Od. Without such training, attempts to use psionics are almost invariably detrimental to a mortal's health, mental health and lifespan.

The result of this is that advanced mortal users of psionics are far more likely than Celestials or Demons to have very concentrated but full-bodied abilities in one or two specific areas rather than a few scattered powers. Mortals are therefore the most likely to consider themselves a practictioner of a specific field rather than a broad-based generalist.

There are roughly as many mortals with the potential to access psionics as demons, but there are more Mortals capable of achieving higher ranks than Demons. That said, because Mortals do not have access to either ascension/promotion or exedis, no mortal has ever managed to surpass the natural non-Celestial ceiling at of Vallus.

Manifestation

Psionics can produce a wide variety of effects. However, it is distinguished from magic not only by its energy source but by its invisibility - unless a person uses their abilities to produce a visual effect on purpose. That does not mean it is impossible to tell who is producing an effect, but that does require either a detection spell or skill in energy reading.

Effect On the User

When properly wielded, a psion will generate and expend energy at roughly the same pace - this speed and quantity of energy one is capable of producing and cycling through is the largest factor in determining the overall strength of the wielder. Provided this balance is maintained, there is virtually no negative effect on the mind or body of the user. However, it is also possible to burn through Od more quickly than it is generated - this is extremely dangerous, as it can cause extensive damage to the body and mind. The damage can even be fatal.

The self-control needed to control this power without harming oneself tends to result in a more disciplined and orderly way of thinking and approach to life. Celestials excel in psionics as the society of Astrum promotes these qualities. However, whether the disciplined nature of Paradisi society creates or is created by their use of psionics is perhaps an open question.