Kingdom Hearts: Ansem's Report 2

It is my duty to expose what this darkness really is. I shall conduct the following experiments:

Extract the darkness from a person's heart.
Cultivate darkness in a pure heart.
Both suppress and amplify the darkness within.

The experiments caused the test subject's heart to collapse, including those of the most stalwart. How fragile our hearts are! My treatment produced no signs of recovery. I confined those who had completely lost their hearts beneath the castle.
Some time later, I went below and was greeted by the strangest sight. Creatures that seemed born of darkness...What are they? Are they truly sentient beings? Could they be the shadows of those who lost their hearts in my experiments?