Prismancy is a subdiscipline of geomancy and luxmancy revolving around crystals and breaking apart light into its different components.
It is very specialized magic and not exactly common. Skilled prismancers can use the properties of certain wavelengths to, say, detect heat and, by extension, living beings, who are out of sight.
Examples[]
Prismancy has a few specific uses in addition to the ones its "base disciplines" have.
Utility[]
Breaking light apart into different wavelengths -in this case, infrared- can effectively be used as heat-vision. The user will be able to see heat emitting from persons or objects, even through walls.
Likewise, turning it into ultraviolet light may make it serve as "blacklight", showing things like clues and filth that aren't visible to the naked eye.
Amping up this ultraviolet light takes incredible skill, but will kill microbes in its light rapidly, rendering the light able to be used to sterilize and prevent disease.
Conjuration[]
Prisms or other reflective surfaces can be created out of crystal to greatly amplify the potency of light-based spells.
"Basic" rocks and, if the caster is powerful enough, soil, can be compressed into crystals, which may be preferred over normal rocks due to their sharpness and tendency to shatter. They can be used for conjuration as with regular geomancy, but are too dense (literally) to be animated without some extra help.
Offense[]
Extremely skilled prismancers may be able to damage other creatures' genetic structure through exposure to radiation, taken from regular light and focused into a single beam.
Like geomancy, the crystal shards can be used for offense.
Known Prismancers[]
Jem is a geomancer and a luxmancer and combines these disciplines into prismancy. He is unable to use different wavelengths, and mostly sticks to crystal conjuration. He might rarely amplify his light magics.