Put this clip early in a scene, just before the threat is revealed, then follow it with the FNAF Jumpscare Scream at the moment of the reveal. For a slower build, place the Inception Horn Sound Effect after the whistle to raise the stakes before the scare lands.
About this sound
This seven-second clip is a thin, wavering whistle that sounds far off, as if carried across fog on a still night. It feels uneasy and watchful, creating slow dread rather than a sudden shock, and makes a listener pause to check what might be nearby. It comes from The Man From The Fog, a Minecraft horror mod built around a tall, shadowy figure that stalks players after dark.