Illusion magic is a school of magic involving the ability to create artificial images either in individual people's perceptions of the world, or one's appearance in any physical property except one's literal, actual form. In the former case, when it affects individuals' perception, illusion magic may be considered a form of psychic magic. Illusion magic is closely related to shapeshifting, the art of morphing one's own form through the use of magic, and together form the basis for maintaining the Masquerade by demi-humans who have forms that belie their ostensible humanity.
Depending on the form of illusion magic at play, it may be applied either to a target whose form is to be masked (the "altered") or a target (either animate or, in the case of mirages, inanimate) which is to behold the illusion (the "illuded").[amend] These terms are not standard, but still useful insofar as the "target" of illusion magic may otherwise be ambiguous.
Forms
As with most magic, different mages and demi-humans have derived various independent practices of illusion magic, most of which coexist with no additional complications. Though illusions are commonly attributed to light, or to its sensory counterpart in animals, vision, illusions may span across any number of physical properties and senses. Different forms of illusion magic account differently for factors such as the discrepancy between the altered's actual and perceived forms.
Psychic illusions
The most common form of illusion magic is psychic, wherein the practitioner creates an image in the minds of illuded targets through psychic powers. The power may be used to form a comprehensive image of an otherwise ethereal being in an illuded target's mind, a common practice with spirits. Furthermore, psychic illusions are commonly used by demi-humans to veil their inhuman traits from humans.
As the latter case introduces the risk of the effect being broken if the illuded target, for example, if they make contact with an appendage the demi-human intends to hide, such as a vampire's pair of fangs or the tail of a lamia, psychic illusions commonly motivate the illuded target to subconsciously ignore all such discrepancies. Many forms of psychic illusions are entirely psychological and do not affect the senses of the illuded target whatsoever, although extensive subjection to such forms of illusion magic may impart a dreamlike quality to any experiences or memories while under illusion magic.
Psychic illusion is usually only self-inflicted and unlike transmogrification in shapeshifting, more often than not cannot be applied to others. Despite this, some practices do allow mages to mask the appearances of objects other than their own, although it is generally not useful as combat magic.
Mirages
Aside from psychic illusions, mirages refer to illusions that affect how altered targets appear to any illuded object, including sapient animals, humans and demi-humans to which magic usually applies; but also including cameras, mirrors and other equipment to which psychic illusions often do not affect.
The name derives from a common real-world phenomenon wherein light may, in certain cases, refract to produce a false reflection of certain objects above or below themselves. The phenomenon, unlike, for example, hallucinations, is tangible and fully visible to all imaging equipment; though when in effect, the actual physical objects at play are not accurately depicted through light. To this extent, the term is also used for the magical practice in Offetstine.
Mirages are used by some demi-humans to hide their forms, although this use is less common than psychic illusions and shapeshifting. More commonly, mirages are used as combat magic, to deceive illuded opponents into behaving in such a manner that they endanger themselves. While mirages are generally considered more robust than psychic illusions, they are usually more complex to maintain than their psychic counterparts, and cannot rely on the illuded target's own sensibilities to make up for discrepancies between the illusion and real world. Furthermore, though illusion is commonly associated with light, mirage illusions often need to span multiple physical properties to create a congruent image.
True sight
True sight refers to the immunity of an individual to all forms of illusion magic. Usually, true sight is itself a magical skill, although some demi-humans and magically empowered humans also have this power innately. Variously, an individual with true sight may neither see nor recognize when another mage or demi-human manifests an illusion before them, or may be able to recognize the failed attempt and see through it. True sight is generally considered a fairly rare and powerful skill.
Certain forms of illusion magic may be vulnerable to more mundane means. For instance, when one's entire form is illusory, a common paradigm for Aetherius demi-humans, the form may be fully invisible in one's reflection, in film or to photosensors such as cameras. This is fairly common with ghosts and spirits, although very rarely applies to any demi-human species that has a biological form, such as vampires. Despite this, species that have biological forms are still vulnerable to exposition if their illusion is psychic.