The Prisoner
The Prisoner at the end of hallway shifted and rolled over on his bed of straw. To the Dementor he was nothing more than a figure, a shadow amongst shadows. There was no face to the man. But the Dementor could feel the clinging thoughts, the hanging tendrils that floated off of the Prisoner's mind. They were particularly agitated today. They swirled around in the shadow, dipping and mixing with one another.
The dementor could tell which moments fit with which huddled prisoner. Except that the Prisoner had the end of the hallway did not huddle. It didn't shrink or turn away. Not anymore. It had stopped after while. And, unlike the others, it hadn't started shivering or shaking. It just sat still most of time. Every once and a while it would grow restless and pace, it's gray form wavering, flickering between the bars.
The Dementor had tried dozens of times to grasp what kept the shadow just a shade above black. There was something inside of him that made him not quite empty, but that the Dementor couldn't reach. It wasn't a white memory; there was nothing sweet or appealing about it. It just was. The Dementor had a word to associate with it. He had lifted it from the thoughts of the shadow once, but he didn't know what it meant.
Innocent.
It helped that the Dementor had heard it once before. From a shadow that had long passed elsewhere. A small, shivering, empty shadow, had been visited by two healthier ones. When the visitors had left the shadow was no longer empty. It wasn't even the same shadow. A new one had taken its cell. The Dementor could remember sweeping down on it, sucking away its pride and its peace. The new shadow had been much sweeter than the old one. There was more that wanted to be clung to. This shadow fought more, made the game more fun.
Two days later the shadow vanished from the Dementor's perceptions. The Dementor had only noticed its sudden absence because of the silly little thought left over. Innocent. The vessel containing the shadow died, and with it died the thought.
The shadow at the end of the hallway was lasting much longer. Twelve season rotations. This shadow persisted.
The Dementor actually wished the shadow would get away. It was most annoying, being unable to finish emptying a shadow. And if the shadow were to get away, it would move into the world full of white shadows. It was cause ripples of doubt. It would stir things up.
In the Dementor's opinions things had been stagnant for far too long.
When the Prisoner at the end of the hallway gained a new grayness the Dementor learned to keep away from it. The new thought wasn't sweet at all; it wasn't even tasteless like the old one. It burned. It was hot; it charred and scorched like the sun. The Dementor stayed at a safe distance in the comfortable cool stone hallways.
It watched the Prisoner occasionally, just to see it stir, and ponder on the new heat it couldn't seem to squash.
The Prisoner at the end of the hallway shifted again. It's thoughts were a whirlwind. Then, suddenly, they began to change. They got smaller, more obscure. But the new one got no less hot. The shadow slipped through it's bars and darted down the hallway.
Not wanting to get burned the Dementor got out of its way.
Besides, it could tell from the shadows taste that it would cause change.
Change, the Dementor considered, would be good.
Very possibly it would be sweet.