The Darkness

The Darkness is an entity featured in the Kobolds & Catacombs expansion for Hearthstone. It initially enters the battlefield in a dormant state, but after three Darkness Candles have been snuffed out, it awakens as an extremely powerful creature.

Speculation
The Darkness and its connection to snuffing out candles is reminiscent of the Devouring Darkness vignette. The Darkness may thus be intended to be a Hearthstone representation of the Devouring Darkness.