Every citizen of the village believes it is a village. They’re right. In every respect except size, the village is a village. Nothing is expensive, nothing is well made. No one is cultured and local culture is strange and backward.
However, the village is one of the larger cities in the area, if measured by population. If measured by geographical size, it is the largest city in the country, if not the world. This is because buildings aren’t often near each other and because it’s rare to see a structure much taller than one man standing on another man’s shoulders. Farms are more common than buildings.
Village energy emanates from them, keeping everyone who remains nearby more than a week under the impression that they live in a village despite knowing how big it is. (This includes player characters.) This is to prevent them from building a plumbing system in its underground home, where its family lives.
The monsters are symbiotic.
They care for plants from below, making the farms and gardens above flourish. This keeps the villagers fed and able to export the best produce in great quantity. They build tunnels to outhouse pits so they can gather fertilizer. They dig underground irrigation. Deep rooted plants (including grapes, the main crop) need no water.
The monsters eat only waste and rotten things. They’re very intelligent but not educated or scholarly. They like the simple life.
They look like radish humanoids. The radish is the head and leaves and roots are the body.
Church of Rot
The only local church is the church of rot. Members collect compostable material and toss it down well-like structures at the front of each church, where other churches might have an altar.
Members believe they are making offerings to an evil rot god underground that will blight everything, including people, if angered.
Some church elders know that the compost donation is for a practical purpose, but they don’t know about the Village-ness magic.