Crystal Quartz

Crystal Quartz is used by both ameshas and devs. For the ameshas who specialize in earth based magic, they are able to tap into the crystal's natural healing energy and amplify it through their body. As a crystal that supports intuition, it is universally useful in almost all affairs, from physical to mental to spiritual. Some ameshas will not make any meaningful decisions unless they have quartz crystal in their hand. The clarity it brings can be so specific that amesha physicians performing complex surgical procedures will let their crystal jewelry guide their hands. More recently, they discovered that by [crafting crystals into their surgical tools , they are able to diagnose and find obstructions to patients health. Crystals are imbedded into all kinds of tools and weapons. Their benefits to ameshas are so strong that they are part of the cultural identity of many amesha civilizations.
Devs on the other hand used crystals in very different ways. As beings who specialize in light magic, their usage is much more visible. An easy dev spell performed while the sun is up is to charge crystal with light. The crystal will hold this light and softly discharge it. it is often cast in the last hour of the sun being up so that the crystal provides a humble light throughout the night. In areas with a lot of magicians, such as the The Temple of Ayeshastra quartz crystal spheres are attached to the wall of corridors and it is someone's duty to charge them them for the night.
Skilled dev users of crystals can create and invest their illusions into crystals. These can only be still illusions, but with a little creativity, they can still change the appearance of an entire space.