Long has (Insert town in your setting) been plagued with the curse of its oldest resident. Every 26 years the being known as “That” awakens to feed after an act of extreme violence occurs in the (town you mentioned above.) While awake “That” takes the form of Dimmingeyes the Prancing Clown, and hunts and lures children in to scare them and eat them. Dimmingeyes has massive control over (your town) whilst awake. He controls the weather, the collective memory of the town’s inhabitants and can only be seen by those he wishes to be seen by.