The Illearth Stone
Years ago a large meteor, presumed to be made of bloodstone, fell out of the sky, and its magical properties were used for healing by the priestesses of the Sentara Temple.
Unknown to the priestesses, an evil spirit from the outer realms inhabited the meteor, and eventually its malign influence led to the fall of the temple. During the fall, corrupted practitioners of blood magic managed to escape the temple with a large foot wide chunk of the meteor intact. This chunk became known as the Illearth stone.
The Illearth stone (and the meteor) were composed of a marble/jade like material similar to bloodstone, however the malign influence of the inhabiting entity caused the normal green/red coloration of bloodstone to become streaked with bright green quartz like veins of power.
The Illearth stone normally radiates a oily unpleasant warmth, causing most normal creatures to feel queasy.