Realmstone is the crystallised, solidified essence of a realm's ruling magic, the single most precious and sought-after substance in the Mortal Realms. Wherever a realm's defining wind grows dense enough, it can condense into physical form, and each realm yields its own variety: amethyst-hued grave-sand from Shyish, gleaming ore from Chamon, living jade from Ghyran, and so on through all eight planes.
Every variety of realmstone holds a fragment of its realm's fundamental power. Shyish realmstone can drain life or raise the dead; Aqshy's holds furious heat; Ulgu's bends light and truth. To those who can harness it, realmstone is a source of magic, industry, and war without equal, fuelling enchantments, powering war-engines, and lending devastating potency to weapons and rituals. Whole economies and empires are built upon its extraction.
Inevitably, realmstone is also a cause of endless conflict. Its deposits are fought over by every faction, mined by the Skaven for their mad experiments, hoarded by the free cities, and coveted by the servants of Chaos and Death alike. Because it is literally magic made solid, realmstone can also be dangerous to handle, warping the bodies and minds of those who work it carelessly. It is the oil and gold of the age rolled into one, and the search for fresh seams drives explorers to the deadliest corners of every realm.