The first time Leo saw one, he was seven years old, hiding under his bed during a thunderstorm. It drifted through the wall of his bedroom like smoke through a screen door—a thing of pale, shifting light and too many angles. His mother, checking on him a second later, walked right through it. She didn’t shiver. She didn’t stop.

Leo understood then. The creatures weren’t monsters. They were the universe’s backlog of ignored things: grief, possibility, the seconds between heartbeats, the shape of a dream you wake from and instantly lose. They couldn’t be killed or blocked because they were already inside. Every wall he built was just a wall inside himself.

That worked fine until the day the creature in the library sat down across from him. It was tall, human-shaped, but with a face like a shattered mirror—each shard reflecting a different version of Leo: Leo crying at his father’s funeral, Leo laughing at a bad joke, Leo asleep, Leo screaming. It placed a hand on the table between them. The hand went through the wood without disturbing a single grain.

The mirror-faced creature leaned forward. “Because you are the only one who ever saw us clearly. When you were seven, under that bed, you didn’t scream. You watched . That made you a door.”