If You Push Nature Far Enough, Nature Will Push Back

The Hallowed Temple of Oot is the only settlement in the densely-floraed region known as The Luxem Theocratic Expanse. The entire region has been heavily forested with all kinds of plants for as long as anyone can remember. This region was the last truly wild and untamed wildernesses on the continent, and every society seemed to subconsciously want to leave it alone. No one has cleared land for settlements or farms, or logged the area for the wood.
Then, one day, a group of priests decided that, since no other people seemed to want to tread there, it would be the perfect remote location to set up a temple in which they could worship and perform their rituals and ceremonies in peace. They constructed a city-sized temple in the center of the region, totally isolated from the rest of the world. The priests worshiped Nature, so their temple blended in with the surrounding landscape, in harmony with plants and with Nature.
Nature did not take kindly to the priests invading their last bastion of unspoiled sylvan refuge. Within the space of about twenty-four hours, every plant and vine surrounding the temple extended tendrils and released spores, and snuffed out all humanoid life in the entire temple. Tens of thousands of people died in a disturbingly fast fashion.
Today, the temple stands empty, devoid of all humanoid life. There are no bodies. No clothing or bones lie anywhere. The tendrils have receded and the spore clouds have dissipated. The temple stands, empty. This place is this world's Roanoke, a hastily-deserted ghost town. Evidence suggests that it emptied very recently and very quickly. What happened to all the bodies? Only the plants know, and they're not talking.
The priests violated the natural law that says, "If you push Nature far enough, it will eventually push back."