A construct creature, based on the idea of trick-or-treating, if there is a festival similar to Halloween in the campaign world. These creatures pretend to be inanimate but very scary-looking costumes and wait until a child puts them on - then they take possession of the child's body and force them to acquire candy by any means possible (first begging, then scaring, and finally attacking people if it's allowed to run free long enough.) The costume stores some of the energy and uses it to gain more power and control the longer it's worn. These costumes were created by a hag and set loose as a way of fattening up the local children for eventual eating, without having to go to the trouble of doing it herself (or the expense of building a gingerbread house).
Art by Steph Cherrywell
Really, any holiday in your campaign world that involves a) people in costume and b) food can have Childcatchers. I can see a similar version for adults.