Challenge: Wasp clerics of life and discord, chemical weapons, and conspiracies. In modern-day Poland.
They have been called by many names. Vampires, demons, even fairies. But in Poland, where the last of them live, they are called the boginki, the little goddesses. They are not human, though they may do a good job passing. They're more like wasps, to be honest. Pretty easily mistaken as wasps, actually, at least until they get too big. Just ignore the pure white color of their shells.
The resemblance is only incidental. Insects they may possibly be, but they're off some entirely different branch of the tree, its only extant members. While they once ranged across Europe and possibly further their numbers were never especially high. They were primitive in their way but intelligent enough to recognize that over-breeding was too likely to lead to their being hunted down (the shadows are only good for concealing you when the shadows are big enough to hold you) or outstrip the humans and leave them without hope for a future generation. Once upon a time their reproductive cycle was separate from humankind, humans made far superior hosts to the point that boginki that depended on other animals were outcompeted. Nobody knows exactly who first made the discovery that somewhere along the line there had developed some defect that prevented their offspring from maturing properly in non-humans, but enough time had passed that there were none who were not so defected.
Instead they left humans to their own devices and turned their natural aggression inward, toward their peers. If breeding was restricted, and any boginka who flouted the rules was turned on by the others in order to keep it from gaining any kind of advantage over the others (kinship loyalties run strong until environmental pressures get in the way), then hostility was inevitable. Conflicts flared in Europe's darkest corners and the population fell and rose again in endless cycles while their culture became evermore intricate and their laws byzantine. In some places the species was rendered entirely extinct, and the boginki more often than not avoided these places, fearing the idea that they might invite the attention of the boginki who had once lived there.
What this led to was a dangerously small population when a particularly virulent plague struck their species. Though spread-out their civilization was well-connected and between the disease itself and the opportunism that followed the boginki were nearly driven to extinction. How long other communities may have survived can't be known for sure, but the only group known to survive into modern times did so in the forests of Poland, restricting itself to the humans that lived therein. These boginki dreaded the world outside the wood as the place where, to their knowledge, the rest of their species had perished, until they half-denied its very existence. Little by little they preyed on each other as well as the beasts and humans of the forest, partly a consequence of the pressures that they were forced to operate under, and their civilization slowly decayed. In the wake of the plague and the ensuring conflicts there were too few boginki to pass on the full extent of their culture. Now there are only faint memories of the past, and a single divinity that they call Marzanna when they speak in human tongues.
But Marzannna does not appear to be a true relic of their former culture, to be honest. She is a Slavic deity, as traditional as they come, and whatever she may have once been to the boginki has been merged with human folklore. She is a goddess of winter and a goddess of rebirth, a goddess of death and the peculiar reproductive cycle that the boginki possess.