Patterns of Life

The existence of magical forces results in a much broader definition of 'life' and how it can propagate. Because 'magic' consists of essentially several additional unified field theories due to reality layer interaction, it's quite a disservice to simply lump them all together into a purely Magical-Mundane spectrum. However, such a spectrum serves adequately through a very broad and mundane-centric view of the world.

Magical-Mundane Model

The magical-mundane model is a very 'northern' (half of the continent) concept, much like that of loose superimposition: it serves to describe the upper half of the continent quite well, but performs very poorly at providing classifications for the phenomena seen in the southern half. Anything dealing with the Plane of Blood tends to break the model entirely, as it's a discrete plane based on physical substance rather than a form of energy. Regardless, the model works as follows:
There are two primary groups of magical creatures: spirits and extaplanars. The reason that biologically-based magical creatures are extraplanar is that there are very, very few creatures which exhibit magical properties without drawing energy from other dimensions. This is due to efficiency reasons: one can get significantly more energy out than they put in when utilizing a dimensional link, while purely internal magic is restricted by conservation of energy at best. Spirits, being wholly magical in nature, are more likely to be purely monodimensional due to being able to optimize internal systems more, although most still rely on other planes.

Extraplanars

Creatures which draw from other dimensions, but exhibit primarily mundane biology. Note that 'mundane' can get pretty crazy, and may be built around materials which require blue quanta to exist.
One might ask why salamanders and arcahe are the only creature within the midlands to access the plane of fire. While other wildlife may gradually evolve to gain fire resistance due to being hunted by salamanders, they never truly make the jump into planar manipulation.
First of all, Salamanders are an apex predator. As a result, there is nothing above them to bio-magnify the fire planar compounds other than humans. Midland humans are notable for being able to breathe fire. Arcahe, another apex predator, have an alignment that is far more subtle.
Second, the kickstarter for gaining planar manipulation abilities was not simple evolution. The exact source is unknown, but there is no mutation that would allow for that original 'jump' naturally. The most likely origin lies somewhere in the Age of Chaos, with some deity modifying their followers to draw from planes that they had some partial dominion over. Pinpointing the time that this took place can be strange and inconsistent between species, given the uneven flow of time exhibited during the era.

Spirits

Entities that sustain themselves primarily through non-physical sources. The key difference between spirits and extraplanars is that spirits subsist primarily on magic, while extraplanars use it as a supplementary source of energy. Spirits tend to cluster around areas with high concentrations of magical energy. Elementally-aligned spirits tend to be either Darkness or Storms-based, as Fire-aligned spirits generally can't exist for very long in most places.
The key defining characteristics of spirits:

• magic based sustenance & metabolism- not simply converting magical energy to calories

• indefinite dormant state when lacking energy sources for sustenance

Common features of spirits:

• hard light markings

• limited decision making ability despite large size

Mediums of Life

Nightmare and spitemongers have as much in common as plants and fungi- that is, while very similar, they have fundamental differences that any rigorous classification system should acknowledge. This is the main limitation of purely relying on the magical-mundane spectrum: it doesn't really differentiate between different types of magic, only the ratio of magical to mundane energy that goes into sustaining an entity.
The Magical-Mundane model is exceptionally poor at handling Blood, as it was designed within a set of cultures in an environment where planes were about forms of energy. The 'medium of life' system is about the base assumption that the mundane isn't inherently different. That is, while mundane-magical treats things as a linear axis, thinking in terms of mediums of life instead places 'mundane' as a single point, equally weighted with other forms of life. These are, loosely:

• storms

• fire

• darkness

• blood

• mundane

• spiritual

• chaotic

A creature can contain any proportion of the aforementioned- for example, mundane humans with no training in arcanism or similar fields are about 95% mundane, 5% spiritual. Midland nobles are ~15% fire, ~70% mundane, and 15% spiritual. Ish.
Note that any one of these can utterly break a purely mundane reality, but act to check on another. Darkness' ability to disregard spacetime isn't world-breaking because everything has a Celestial component, for example. There's an argument to be made that they don't always balance one another, hence the existence of elemental planes where one particular force overwhelmingly dominates.
Each has several sub-categories: for example, mundane life can be plant, animal, fungus, bacteria, etc.

Spiritual (Celestial)

The spiritual medium of life visually manifests as hard light in its pure form. Everything with a soul has some spiritual component. Celestial flubbing is a less obvious form of the spiritual medium which integrates less obviously into other mediums. Note that it does physically manifest even in humans (who aren't casting arcane magic): eyes shine with the color of one's soul.
The spiritual/Celestial medium is highly compatible with others, existing in all entities with a soul to some degree. It almost never exists in a vacuum.
Differing orders of soul aren't fundamentally different mediums. However, they do result in different functionality.

Blood

The medium of Blood most typically takes the form of, as one may expect, blood. In a more abstract sense, the medium is about organic matter which doesn't act as it normally should. Blood is a rather challenging medium of life to isolate because it's intrinsically tied to its physical form. While the medium of Darkness may work to puppet an object, it isn't the object in itself, and can be cleanly separated and analyzed. Further adding to potential confusion is that the medium of Blood doesn't just take physical form, it takes physical form identical to existing organic matter- however, said matter simply doesn't behave anywhere close to the way that one may expect. On a molecular level, below the coherency limit, analysis may show the material to be such. However, on magical scales, all of the material's properties are dictated by Blood rather than conventional physics. Blood also tends to exhibit the ability to selectively apply its base material's properties as expected, such that efficiency is improved. This is also why the Blood medium's base material even matters: it dictates what sort of properties are more efficient to maintain.
As a general rule, the more intelligent a Blood-entity is, the lower its proportion of Blood to Celestial. Ghouls, for example, typically have an almost 50-50 split between Celestial and Blood. Clots, mindless lower-tier blood spirits, are almost entirely Blood.

Darkness

Exists in the space between things. Note that the Plane of Darkness is an interesting Greater plane in that its fundamental force is inherently non-mundane in nature: the Plane of Fire is associated with thermal and electromagnetic energy, while the Plane of Storms is mostly around kinetic and gravitational, more or less (as a simplification). Darkness is built around negative light , a concept enabled by blue quanta: non-Primordial, unlike the other two.
Darkness is very hard to destroy- typically orders of magnitude harder than destroying its anchor.
A lot of Darkness doesn't care about spacetime in the way that mundane things do; while not outright apart from causality like Chaos can be, the concept tends to have a certain irrelevance to the medium of Darkness. On the other hand, it's more easily influenced by Celestial force. This translates to quite a few different effects. Immortality, a consequence of ignoring time. Spatial warping, a result of ignoring distance: commonly seen in shadow spirits like puppeteers and nightmares. 'Folding' abilities like Vhagar's Shadow.
Much of sorcery involves the creating and manipulating this category of life. Sorcery
Cotd contain varying amounts of Darkness- every generation progressively increases the amount of Darkness that a Cotd contains, and soul energy is spent during gestation in order to establish stability.

Celestial & Chaotic

Two subcategories for Darkness mediums specifically adapted to deal with particular types of magic. Darkness' nature of being somewhat apart from the mundane reality lends itself well to interfacing with either non-mundane reality layer.
Celestial Darkness is a rather interesting medium because generally speaking, high proportions of Celestial mediums result in reduced ability to draw upon other planes: cross-planar magic is Chaotic by nature, which can't directly interact with Celestial energy (being two realities away). Constant transmutation of Celestial energy into physical forms that can interface with cross-planar magic results in much reduced efficiency; often more of a byproduct than a primary objective. Celestial Darkness differs due to the lingering nature of Darkness. While still technically inefficient to transmute, smaller connections to Darkness are more useful than to other planes because the energy drawn from Darkness is naturally much more inert than that of Storms or Fire, making it much easier to contain. In the most basic, literal sense, drawing from Fire in the way that one does from Darkness would result in a constant, small trickle of heat and pressure. Without a physical vessel to contain this until sufficient pressure can build up as to be useful in some way, it's useless. However, the very existence of a physical vessel implies a significant portion of physical (non-Celestial) life force in the first place. Same goes for storms and air/water pressure (and water's only useful if one has biological systems anyway). Electricity's a bit easier to contain because it can be relatively efficiently be converted to Celestial energy (remember that Celestial energy by default manifests as light, something on the EM spectrum). Darkness' natural pooling effect means it naturally wants to linger around its source. Sorcery mediums largely take from the Celestial side of things, as they're made through the caster's will. The main exception to this is silencing. Sorcery:Silencing

Storms

Tends to form a shroud surrounding other mediums rather than directly mixing with them.
Very high mundane information density and processing.

Fire

Fire is practically more of a disease than a medium of life- its propensity to consume basically means that the rest of the entity is constantly working to avoid being eaten by itself.
All in all, wholly unsuited to sustaining life. Doesn't lend itself towards sustaining in general, really.

Chaotic

Generally considered unknowable.
The chaotic 'medium' can almost be defined more as an absence of life.