Pure, by V. L. Draven

They sought purification, to make the world a place of good, a place where only the light would shine. But, darkness is not the absence of light; evil is not the absence of good, and as darkness can shine as brightly as the strongest sun, so evil can be as pure as innocence. They did not realise that their desire would be the end of all. They released that which was imprisioned in the void and set it loose upon an unsuspecting world. People screamed as they were consumed by impenetrable darkness that sucked away their souls; Earth became pure.