I've typed it before and I'll type it again: there's no such thing as too many resources for a GM, especially when it comes to monsters to throw at your party. Folklore: Creatures of Myth and Legend takes its inspiration from real life, or, at least, the stories we tell in real life. Myths, tales, urban legends. They're filled with all manner of crazy beasts and horrors, and that's just what you'll be getting. The book is up on Kickstarter now.
From the campaign:
Folklore is a collection of beasts, legends, and other things that go "bump" in the night for Fifth Edition roleplaying games. The 50 creatures of Folklore are inspired by real-world urban fables and classic tales of terror, with pepperings of completely original monsters that are sure to terrify. What sets Folklore apart from a traditional monster supplement is that the monsters of Folklore will come hyper-detailed with their own sets of lore and legends, as well as ideas and prompts for encounters, scenario hooks, and other original ideas for each spooky species! This tome of beasts aims to fully flesh out each monster into a tangibly terrible entity -- so real you swear it could be right behind you…
Folklore is a unique creature codex based off of tales about the monsters in world. Our goal is to bring the most unnerving, bizarre, and interesting creatures into your 5th edition games. We are also creating some original beasts conjured from the darkest places of our minds, inspired and fuelled by the spirit of folklore. We don't plan on simply dropping a book of random stats for obscure monsters from around the world on your lap; we're dissecting them and making them useful for your own diabolical purposes.
The campaign is making its way to 2x funded with still 14 days left to go.