Noxite

A diamond or luxite gem that absorbs too much negative energy can turn into noxite. This gem seems to absorb light, making the area around it darker. The rituals to turn luxite into noxite are only known by the most powerful necromancers who find it supremely useful for channeling necrotic energy. An evil-aligned creature can replace diamonds with noxites of the same value as the material component for a spell.

By casting Negative Energy Flood on a piece of diamond or luxite once for every 1000gp it is worth, it is converted to noxite.