"The coins are made of pain," says Juliet. "More of it gets a pointier coin and a bigger wish. Whistles love it like candy; Sherlock liked it enough that it didn't take a lot of magic to get her to hexagon- and star-making on the regular. Most Bells - though not me or Angela, we come from totally nonmagical worlds - have a sort of inborn mental opacity power that won't let anything alter our brains, and even me and Angela don't like the idea, so even we take help where we can get it."