Sepherim Cromwell, a Dark Lord with wealth beyond measure and overwhelming power and infamy, known as the 'Demon King' ruled over the Underworld with an iron fist. But his Seven Dukes betrayed him and left him for dead.

With his dying breath, Lord Sepherim scattered the shards of his essence throughout the underworld. "Whoever can gather these and reunite them will become the next Demon King."

Many have searched for the shards, for possessing even one grants power. Those who possess these shards are known as Grimlords.

But none has yet managed to unite them all.

Zac, brutally murdered by monsters and sent to the underworld, has only one hope for survival: he must find Cromwell's shards and become the next Demon King.