Starstone
Starstone is a living mineral created originally on the Illidian homeworld during the Fourth Universe. It has unique properties that change, depending on its state and refinement.
Natural starstone is a white, opaque crystal. Given enough time, a single piece of startstone will grow and expand, converting the surrounding material into more starstone.
When the crystal is purified, it turns to a black color, which brings out flecs of white within. This form resembles the black of space with a mottling of stars throughout. Purified Starstone was used in Illidian construction of buildings. Due to its rarity currently, it is more recently used as jewelry among the most wealthy and powerful Illidians.
Imbued Starstone turns translucent and takes on a blue hue and glow. In this form, the Starstone takes on a form of sentience with a purpose of testing the worthiness of Bin Tamabd to ascend out of the prison of causality and mortality. The process of imbuing starstone in this manner was lost with the disappearance of Tyr, although a large mother stone exists on Avalon. This motherstone is the source for all starstones used by the Illidians, including the creation of the Temporal Codex.