He felt a very distinctive emotion now radiating off the human and the pokemon; fear. Thats what he was going for alright and kept his power into the crystals, making sure they made more noises and shadows.
How he could still manipulate the crystals to his liking to scare off those that wandered into his cave, it worked each and every time. There was no possible way that this could mess up. That…till he moved one of his legs onto some loose rocks. Before he could catch himself with his own psychic energy, the pokemon slipped and fell to the ground, a heavy thud ringing out through the cave.
The shadows on the walls and the noises soon stopped as the sudden thud was heard, making Mewtwo actually cry out in pain. Oh how he wished he could see, thus preventing this from happening. But he grunted and laid on the stone floor, trying to get himself up to no avail.
Rebecca winced at the loud noise, pulling off her headphones to save her ears. Sometimes she hated echoes with a passion. When the echoes died down, she put her headphones back on so she could hear again.

“Ugh, ow. I hope who or whatever just made that sound is alright. Even if it’s the monster that lives in this place.”
Rebecca pried Triton off her leg and continued into the cave, making sure to look carefully at the walls for any crystals she could take.