"The potent and foul magic that accompanied the demons from their world into our own seems to be quite capable to sow malice where there is none to be found. In this particular case - in rocks. Not quite aware, these self-propelled, magical boulders seem hell-bent on smashing anything - both at a distance and close by - that makes the mistake to cross their wandering path."
The Essence of Rock tosses boulders from distance and attacks with smashing blows in melee, similar to those of a Gargantuan Spider, requiring a flexible strategy and good timing to avoid them. Upon destruction, it splits into three Essences with charge attacks that knocks back, but are quite predictable.