Chimaera

The fame of the chimaera that haunts the village of Nevynnera spreads far and wide. As the rumour has it, the beast comes out once a month when the moon is full and rampages across the livestock, slaughtering chickens and cows alike. Whenever the monster runs rampant, the beast in the surrounding area hide and dare not approach the village. Occasionally, half-eaten wolf carcasses and parts that can only come from bears are found among the slaughtered livestock, implying the chimaera goes out into the woods and hunts much more than village game.
During the Age of Heroes, not one and two brave adventurers that heart the rumours have tried to slay the nightmarish beast. Most failed, and paid with their lives, but even when some parties seemingly succeeded, it always came back after a few full moons. Attempts to contact the larger forces and involve greater powers into the deal have gone unsuccessful
For the past century, now that adventuring is a dead business, the people from Nevynerra have all but given up on their attempts to drive off the menace. They purchase more livestock than their neighbouring settlements and are content as long as the beast doesn't harm any of them, which it is seemingly not interested in.
Of course, as legends go, the truth is much, much different... and far more disappointing:
Centuries ago, during the dawn of the millenium known as Age of Heroes, a small family decided to settle in the ruins of Nevynnera's Fortress and make it their new home. Driven by viking raids from their homelands, they recognised the area was primed for farming, with perfectly green grasslands surrounded by thick forests. The reason that the area was uninhabited was the legend of the chimaera that terrorised the lands and razed the keep itself. Disregarding the old stories, the Boltens decided to renovate the east tower of the once mighty keep. They didn't have the resources or the numbers to do more, so they ransacked the rest of the keep for stone, and cut wood from the nearby forest.
The new keep was quite small, but it was enough to house and shield them, and once it was rebuilt it started to attract the attention of local villages. Selling whatever valuables they salvaged from the ruins in the nearby market, they made enough money to buy some small livestock and started running a farm. Over the decades, they prospered, and more farmers from the surrounding villages relocated to the considerably better conditions around what the Boltens were calling the Village of Nevynerra. The stories about the terrible chimaera were openly laughed at, and the are prospered with trade.
The sons of Gavrael Bolten, the family's elder at the time of settling in the ruins, continued to salvage the old keep and improve on their little tower over the years. Once the roof over the heads was secure, and the walls were reinforced to fend off bandits, they turned their attention to reinforcing the foundations. That's when they found the old dungeons beneath the east wing of the former fortress. There were cells upon cells, filled with all sorts of remains, from human skeletons to more... unique creatures. Wolf skulls were found aplenty, and sold for coppers at the market, to drunken hunters who wanted to fool their wives with old bones presented as fresh trophies.
Among the garbage, there plenty of books found, apparent research journals of primitive alchemists, that were working on the transmutation of living creatures. In a collapsed part of the dungeons, the three brothers managed to uncover several closets, stocked full with massive glass jars, filled with liquids and... body parts, of all kind. Human and animal alike. It wasn't long before they made the connection - the chimaera of the legends was created by the original inhabitants of Nevynerra's Keep, and it was purposefully let loose among the people in order to feed. As most of the research was intact, and with plenty of resources to start the experiments anew, the brothers decided they could use the power of a beast as terrible as the one in the stories in order to grow rich and powerful, like true lords.
They didn't know alchemy, but they also didn't need to know to know too much - all of the steps and requirements were dutifully written down by the ones before them. Unsuccessful in their own lifetime, they solemnly swore their sons to continue their work. From young children, they gathered what coin their family had and sent them to the prestigious academy in Emor, from which they returned as at least semi-adequate alchemists. They were able to improve on the original "designs", and it wasn't before long that the nine brothers and sisters had a baby chimaera beneath their "keep".
The beast liked to slumber for almost a month at a time, but whenever the moon grew full, it awoke, and had to be fed. Originally they just released small livestock into its cell, but the more they fed it, the more it wanted to eat. They started letting it out, taking it to other farms in the now sprawling village, in order to keep it from growing too hungry. Like most beasts, they found that chimaeras are surprisingly great pets when satiated.
The villagers noticed their decimated livestock, of course, and as the damage to their farms was growing, so was their discontent. They demanded answers and a solution from the mayor (Gavrael the Third) and threated to abandon everything, fear of the mythical beast reawakened among the area. In a flash of brilliance, however, the Boltens unveiled the tamed beast before the rest of the villagers. Before they had a chance to flee at the ugly sight of it, they were reassured that it was completely under control. They told the elders of the village about how they came to acquire this beast, and that they would use its power to stay safe from any force that could threated their ways, and grow richer and richer in the process. The people liked the idea of being rich, and decided they were more than happy to trade a few livestock every now and again for having the beast around.
They were all sworn to secrecy, and later a young member of the Boltens decided that it would be even better if the reverence of the beast were turned into a cult. During his lifetime he started convincing more and more people into worshipping the chimaera, and bound his sons by honour that they would do the same. A few generations later, the entire village knew only one thing - that they were to take care of the great beast, that would in turn take care of them. They happily sacrificed livestock when it came time to feed, and awaited the privilege to feed it themselves when they were too old and too big a burden on their family. There is no graveyard anywhere around Nevynerra.
Whenever outsiders came, they would pretend that everything was normal. For he who knew that the beast could be controlled, would seek to control it. Whenever somebody was close to finding the truth, they would poison him if he was staying in one of the village's taverns, or collectively murder him in the dark of night. They would put out calls for adventurers to slay the beast, so they could feed it its favourite dish - human flesh. And take all the adventurer's possessions for themselves, of course. Seeing who could attract and kill more people was one of the main sports, and a fierce competition, with deadpools aplenty in the taverns.
Occasionally, an adventurer or a party of such would actually slay the foul beast. They would be left alone, of course, for the ruse only worked as long as people thought they fell to the chimaera. But they would promptly create another one, and raise it with frightening care and devotion.