The children know his name, but they don't say it. To say his name is to call him, and you only do that if you really mean it - if you really need him. Those are the rules.
(The adults didn't believe, not at first. Their children had simply been lost, and afraid, and their imaginations ran away with them. Only when enough bloodstains had been found, when enough parents caught their children conversing with shadows, did they begin to wonder.)
He only comes to children - to the lost, the endangered. The ones who can't run to safety are found sound asleep wherever they were being held, small peaceful islands at the epicenter of absolute carnage. They never wake until they're brought somewhere safe.
(The Sleepers, as they came to be nicknamed, were never quite the same afterward. There was always something about them lying just under the surface of their young, somber faces.)
He is not infallible.