Elemental crystals are a rare form of elemental deposit which occur on realms rather than solely in the Sora. They have numerous uses, the most notable of which is the enhancement of magic.
Elemental crystals appear as small, rough crystal clusters of varying colors. Each color corresponds to a different element or demielement, such as red for fire, blue for water, or yellow for lightning. Similarly, each base element contributes some other aspect to the crystals; fire causes them to be warm to the touch, water causes them to be smooth and slick, earth makes the crystals cloudy, air makes them lightweight, nivose causes a tingling sensation when touched, while fuliginous causes a numbing sensation when touched. These features make the crystals identifiable even if the colors are obscured.
Elemental crystals are incredibly rare, with most realms naturally containing no more than a handful. They are the remnants of the chaotic elements that collapsed to form the realms they occur on, through a process that is not understood by scholars. They are then distributed in small pockets underground. Each pocket typically contains no more than a tonne of crystals in total and even larger realms contain a dozen deposits at most. Smaller realms may have less or even none at all. Discovery of these deposits can thus provide a huge influx of wealth to the realm or nation which uncover them.
Despite their relative rarity, a few extremely large deposits of elemental crystals have been found. The largest of these is on Mieda Norcal, a minor realm in the Heshian Syndicate, while other large deposits are found on Lumiere, Ildathach, and Fœbepføpt. These deposits are of great strategic importance to the controlling empires.
Elemental crystals have numerous uses in a variety of fields. The most famous and spectacular use is to fuel and empower magic. When a person is touching an elemental crystal and casts a spell which incorporates the same element, the spell will be greatly enhanced. The exact method in which is is empowered can be somewhat random; it may have a larger area of effect, be more difficult to resist, last longer, be more destructive, or any other number of effects. Using the crystals in such a way can drain them of their elemental infusions, causing them to shatter and become inert dust. Despite this risk, many mages seek out the crystals for this use. Those who use multiple crystals over time eventually learn to control the effects of drawing on the crystals to empower their spells.
Less known, but considered much more important to those with the knowledge, is essentially the opposite effect. Elemental crystals can absorb the energy of their elemental opposite, greatly reducing or even entirely countering magic which uses that opposite. Similar to using them to enhance magic, this usage to cancel magic also drains the infusion, eventually destroying the crystal. These crystals are valued by the powerful, influential, and wealthy to protect themselves against those who would use magic to harm them.
In a similar vein, elemental crystals can be used to protect against raw elements. One method is to grind a crystal into a fine powder, which is then used to create a glaze which can be applied to objects. These objects will then be protected against the elemental opposite. This use is vital for exploration of the chaotic Sora, outside the eddies and nebulae. Such an activity is incredibly expensive, requiring a great number of crystals, thus it has not been put into practical use at this time.
The crystals can also be used whole to quell elemental eruptions. Placing a crystal into an eruption of its elemental opposite dissipates the eruption, though it invariably destroys the crystal. This can be used to prevent incredibly destructive eruptions, such as calming a volcano with an ice crystal or dissipating a tornado with an earth crystal. Many large cities which potentially face these dangers often keep a small stockpile on hand for disasters.
Elemental crystals can also be used in the creation of magical items, serving as power sources for enchantments which produce or rely on the element. The crystals are often cut or polished to turn them into gemstones prior to use this way, though this can somewhat diminish their infusion. When used in such a manner, the crystals tend to be stabilized through the other magics which hold the item together.
Other uses have been discovered, but are currently considered inefficient or without practical application. For instance, pure element can be extracted from elemental crystals, but currently the process results in only a small amount of usable element, almost always of lesser value than the crystal itself.
Entry for Worldbuilding Summer Camp 2020
Answering: "Describe a material in your world that is used as a source of fuel or power."