IMC, one of the villains is a fey called the Shadow Man who is fascinated by human fears and wants to study them, much in the same way that sith are fascinated by death. (Especially fear of the dark. Why in the world would anyone be afraid of the
dark, anyway?) Because he's so interested in fear, especially perplexingly simple fears like fear of the dark, I figured that he would probably have a reputation in some nearby domains as a bogeyman who frightens children, so I'm giving him a rhyme bane.
As a twist on the rhyme bane, though, I wanted to make it a clapping game, like Concentration or Big Booty if any of my fellow summer camp survivors have ever been forced to play those.

In the game, the children clap rhythmically and list things that they claim to be afraid of, the idea being that the Shadow Man will hear their fears, realize that he's already studied them in someone else, and leave them alone. This appeals to me not only because I love the image of my PCs suddenly dropping all their possessions to play patty-cake whenever they think he's approaching, but also because I think it would be a great source of tension: how long can we keep him at bay until someone misses a clap or can't think of a fear, and the effect is broken? (The bane is also a bit of a double-edged sword, since the Shadow Man can make a Sense Motive check to see if they're actually afraid of the things they're listing; if one of them interests him, then he knows exactly what to start studying when the game breaks!)
I'm not sure what the mechanics should be for the game, though. If it were White Wolf, it would be Dex + Wits, but I don't know what a good equivalent would be for d20. Concentration is too specifically geared toward spellcasters, and a straight Int or Dex check wouldn't cover either the hand motions or the quick thinking. Does anybody have any thoughts on this?
"I'd really love a cup of tea, but it would be, like, blood or death or evil or something."
~Matteo Brazi, Borcan thief, Day 3 of Bleak House