When I was building the world for "Sleeping with Ghosts," I was combing the Balkans and the Carpathians for creepy creatures and means to destroy them, from ill-born children who devour their families to the cold efficiency of iron spikes. There are superstitions in Greece and Bulgaria and Macedonia about how to keep children from devouring their families, or to recognize a human intelligence in a wolf's eyes, or how to know a witch in time to keep her from spiriting you away to Hell. The folklore of these lands is one in which anyone, even and especially your loved ones, might be a monster.
While it's fun to take a mythology and replicate it, to build a culture where vampires or witches are real and follow a particular set of rules, it's also important to engage with the questions that a mythology asks of the people who believe in it. The theme of paranoia and ubiquitous monstrosity is what I set out to explore in "Sleeping with Ghosts," and I'd like to spend more time with it as I start writing a novel (novella?) set directly after it. "How far will we go to detect monsters before they can do harm, or to prevent monsters from coming into the world?" these projects ask. "Will we become monsters ourselves?" From the Callicantzaros page on Monstropedia:
To prevent an infant of two mortal parents born during the proscribed Yule Tide season from becoming a callicantzaros, the infant was sometimes held feet down over a fire by one of the parents until the toenails were singed.
Some people, apparently, were willing to go quite far indeed.