The Radioactive Demon Cesspool

First off, you're probably wondering why anything would be called 'the radioactive demon cesspool'. Well, that's because it's just what someone called it once, and the name stuck. Boring, I know. As for what the RDC is, that's a bit harder, and definitely more interesting. 'It' is more of a 'they', and they are what appears to be invisible formless beings of pure evil. You can't see them, but you can somehow tell exactly where they are and aren't. Like you can draw an outline in the air around where they are, even though they're undetectable by any normal means. They're sealed up in the farthest reaches of the mindscape behind a massive iron door with billions upon billions of tiny interlocking mechanisms covering the face of it. They never stop moving, and no one can figure out what they do, or where the door came from. There are, however, tiny points in between the mechanisms where one can glimpse the inside when it moves just right. I've seen the other side of it, and there's nothing but the deepest, darkest lightlessness one could possibly fathom, undulating slightly. When you look inside, however, they notice someone at their door, and swarm at it. The movement creates a sense of great wrongness and dread like a tsunami crashing though you and everything unfortunate enough to be nearby.

If they would just writhe behind their door, all would be fine and well, but recently, that assumption has been upset. At least four of them have been able to venture beyond the door. Their voices are so impossibly huge, and yet at the same time, completely silent. Like the voice of a god booming inside your mind. They don't yell. They don't need to. They speak calmly, with voices like thunder, drowning out your own thoughts. If I were in my right mind, I would have been terrified. But the first and only time I've ever met them, I was trying desperately to save a dear friend's life. I yelled and swore at them. They seemed amused by it.

Helyx was the one found the door and those behind it some years ago, and that was the one and only time anyone has ever seen him afraid. And that scares the hell out of me.