Grimm gave a shout as he hacked at the crystal and metal rock with his Hydra Greatsword.
The loud sound of the sword against the rock rung in his ears while the rock bore no mark of damage at all. God knows what it was made of and with what sort of processes. It bounced off Grimm's attack when it had been eroded already.
Nonetheless, the echoes foretold something—the space beneath the rock was hollow and sounded huge. Big surprise.
Grimm walked around it and found a crack on a corner of the rock. It looked like a natural mark caused by geological changes over time. He cleaned the surface of the crack with water which he produced by pulling off some sorcery and an entrance to a cave appeared.
He did not rush into the cave. Instead he sniffed by using his enhanced sense of smell. The smell of earth gushed out, combined with something giving off a repulsive rot. It carried the smell of ancient properties in an enclosed space.