My Pet Rock (itch)

A child stands before a dungeon, mysterious and full of odd creatures and twisting platforms. Their only companion in this trying temple? A rock that some old guy gave them. 

Its got eyes though. Weird. 

Defeat all the critters inside a level, and the rock evolves! What will you find at the end? How far will strange science take you in this tale? And where did that old guy get that rock in the first place? Some answers found inside!