Kingdom Hearts: Ansem's Report 5

To study the Heartless behavior, I picked one out for observation. It wiggled its antennae and, as if sensing a target, headed deep into the castle. In the deepest part of the castle, its antennae began vibrating, as if searching for something. Suddenly, a strange door appeared. I'd never known of its existence.
It had a large keyhole, but didn't seem to be locked. So I opened the door. What I saw on the other side mystified me. What was that powerful mass of energy? That night I observed a great meteor shower in the sky. Could it be related to the door that I have opened?