"The Legend of Night Shadow" by Jennifer H. Berry (A shadow of the night)

Once, a long long time ago, when the elements of the world had a life of their own and controlled the forces of the lands. A time when there were only the four great races. A time when wizards and sorcerers battled battles that could change forest to desert with a mere thought. There was a magician named Grakadyic, one of the most powerful.
    No creature of the magics at that time was satisfied with what they had, and Grak was no exception. He sought to increase his domain; he sought to rule the world.
    He took all the magic around him and it wasn't enough, he stole magic form others and it wasn't enough. If he was to accomplish his dream he would need more, more.
    Then he discovered the power of the shadows, a power never before known of, never before harnessed. He drew that power to him, the friction produced was enormous but Grak withstood it, as all others paused to watch. He pulled the power and trapped it within a stone, locking it away. Now he had his power, as much as he could ever want.
    For 50 years he increased his domain, battling others that must give way before him. He was so close to his dream.
    But Grak, for all his power, was still human. Humans cannot live forever. Grak, so caught up in the drug of power would not acknowledge his old age, his weakening. He was playing with powers he didn't understand, he made mistakes. One mistake caused a backlash of power; his weakening body could not contain it. And so the great Grakadyic fell, as all mortals must. But with his dying breath he vowed his fight would not be in vain and he passed the great shadow stone to his only son, who was magicless, seeming magic did not travel by blood.
    But his son could not use the stone. The forces where too great, he did not have the power necessary to control it. He attempted to call its power, not knowing this. The power was unleashed, but not controlled. The shadows broke free and the stone shattered in his hand. Caught in the centre of the magic storm, the backlash should have killed him, and the power of the shadows should have returned to what it had been.
    But the power of the shadows where now concentrated in one place, they could not dissipate quickly enough. That much magic in one place needs to earth itself
    It earthed itself through Grak's son, whose name is not known.
    It changed him.
    Mutating him.
    Creating a creature of the night.
    A creature who controlled shadows.
    A creature known ever after as...

Night Shadow