Small Favors by Erin A. Craig

Ellerie Downing lives in the quiet town of Amity Falls in the Blackspire Mountain range--five narrow peaks stretching into the sky like a grasping hand, bordered by a nearly impenetrable forest from which the early townsfolk fought off the devils in the woods. To this day, visitors are few and rare. But when a supply party goes missing, some worry that the monsters that once stalked the region have returned.

As fall turns to winter, more strange activities plague the town. They point to a tribe of devilish and mystical creatures who promise to fulfill the residents' deepest desires, however grand and impossible, for just a small favor. But their true intentions are much more sinister, and Ellerie finds herself in a race against time before all of Amity Falls, her family, and the boy she loves go up in flames. -Goodreads