Shadow and Illusion
Shadow and Illusion: An introduction to the mechanics of Shadow Matter Illusions
Oorayv'levena, Archmage of the Ebony Order of the Moon
To begin to understand the mechanics of shadow matter illusions, one must first understand the nature of shadow. Explaining the Plane of Shadow in detail would go beyond the scope of this article, therefore I will suffice with a brief introduction [1].
The Plane of Shadows overlaps the entire Material Plane, and can be accessed with the right spell or ability. We can see into it wherever a shadow is cast by an object blocking light. However, it is also possible to enter the Plane of Shadows here, and then travel through it to other realms beyond. In technical terms, we say that the Plane of Shadows is at the same time coterminous and coexistent with the Material Plane.
The substance we know as "matter" in the Material plane has a parallel in the Plane of Shadows, which we could call "shadow matter"[2]. It can be shaped into anything that our primal matter can, and functions in much the same way while still in the Plane of Shadows. However, when drawn out into the Material, it is much more fleeting. If left unchecked, it would dissipate into the environmental shadows. To most, it would seem insubstantial: try grabbing a nearby shadow, you will likely be disappointed [3]. But on the other hand, one only has to be on the receiving end of a punch from a shadow to know that shadow matter can indeed be tangible and have an impact on matter. In analog to this, there is primal energy, and shadow energy (e.g. real fire and its shadow coutnerpart).
The most commonly spread use of shadow matter is in the various types of Shadow Conjuration and the Shades spell. In all of these spells, shadow matter is drawn into the Material from the Plane of Shadows, and then shaped to emulate a Conjuration or Evocation spell, for instance, a Fireball. The fireball created in this way acts just like one created by the Fireball spell, except that it is shaped from shadow fire instead of real fire. This will show in the way the fireball will dissipate, and more directly, in the fact that divination spells have an effect on how a victim of the spell is affected in the case where it concerns a Shades fireball. All shadow matter and shadow energy spells fall into the Illusion school.
The Shadow Matter Illusion specialisation [4] is an extension and perfection of this technique. Instead of learning one Illusion spell with a handful of different uses, a Shadow Matter Illusionist abandons the casting of real Evocations and Conjurations altogether. Instead, an Illusion version of the original Evocation or Conjuration is cast, allowing the mage to use their expertise in the Illusion field to the fullest.
That sounds simple enough, but it is not all there is to it, otherwise they would severely cripple their power against foes that are immune to mind magic or that have True Sight. To overcome this weakness, shadow matter or energy (depending on if the original spell was a Conjuration or an Evocation) is woven into the illusion, to give some real impact, and add effects that lend the rest of the illusion more credibility. If a victim does not spot that the spell being cast is an Illusion, they will feel the full extent of the spell. Of course, the effect on victims that see through the deceit is not as great as it would have been with a normal, real Evocation, but it will still be considerable.
For those who think Shadow Matter Illusion fireballs can be cast without worrying about the furniture, I must disappoint you: I know from experience that a shadow Combust causes scorching in the carpet that is just as annoying as those from an Evocation Combust.
Shadow may be fleeting, but it is still very real.
[1] For those interested in understanding the Plane of Shadows in greater detail, I can recommend the series on the Transitive Planes, specifically part 2.
[2] Also: Shadowstuff.
[3] With enough training, one might actually succeed in grabbing nearby shadows, but the technique is not something that can be conveyed through literature.
[4] This is a specialisation that requires dedication and study of the Shadow subschool of Illusion (the other four are Figment, Glamer, Pattern and Phantasm). Not all Illusionists are the same, and not all may find this technique to suit their personal casting methods.