Voidprism

A rare crystal that grows in places where the void touches another plane. The crystal is shaped like a dark purple, almost black, orb with spikes protruding from it.  It is said to be created from mana and dust that is exposed to the reality-warping laws of the void. At first glance, it will seem as if the crystal emits a dark purple glow, however, upon closer inspection, it becomes clear that the crystal does not reflect light. Instead, it seems to absorb the light in its nearby surrounding, being less efficient in drawing in the wavelength that corresponds to purple light. As a result, it actually darkens its surrounding, which makes the crystal seems distorted. This would also imply that voidprism isn't actually colored a dark purple, but any light that would reflect off its true color is drawn in by the crystal. 
Voidprism can be used as an efficient catalyst in attunement rituals. How it achieves this is unknown, as the abyssal energy it consumed plays a big factor in the process; a type of energy of which little is known. Any additional applications for the crystal have not yet been discovered. The crystal can retain its properties for a few years when taken away from the void before transforming back into dust.