Once upon a time, there was a wonderful place called Bay Nine. It was like many other cities of its time, and some even considered it to be superior. No one wanted for food or shelter, and they prospered from the huge amount of trade that went through their port. Life seemed perfectly normal, and normally perfect.
Except for one tiny discrepancy.
There were a few more querns than a normal city usually had.
Of course, the few crazy people that actually notice these types of things wrote it off as a quirk, nothing at all dangerous. Due to some strange circumstance, Bay Nine had attracted a large amount of people that liked that sort of thing. Some people even went into the business for creating more querns.
Unfortunately, as more people started to make the things, more quern-fanatics were drawn to the city. Walls were engraved with querns within querns, in an infinite recursion. People stopped creating food or other necessities, as the whole economy shifted from a Byzantium trading center to a quern production plant. Why make spirits, or grow plants, when one could just trade a quern for it?
Then the baron arrived. He loved shells, black bronze, and... querns.
Drawn to Bay Nine from rumors of the querns that were created there, the noble was the biggest quern-lover of them all. As such, he demanded that no more querns be exported.
Trade stopped completely, food stocks ran low, and the crazy quern-makers kept on creating querns with glee. Transcending legendary masons, they became... legendary querners!
As the dark clouds gathered over the city, and bit by bit the stockpiles were overrun with the useless furniture, the remaining inhabitants forgot their original lives, their hopes, and their dreams.
They could remember only querns.
More and more were created! The populace was drawn into the workshops like water down a drain, and their creations were flung out into every available space! Walls, floors, tables, chairs, and even querns were broken down to make more, and the very foundations of the town were corrupted by the ever growing menace.
Dwarves started to make querns out of other dwarves.
Fortunately, querns are not known for their structural integrity, and the whole city collapsed into itself before the menace could spread.
Ironically, the quern mandate ended a few days before the city collapsed.
It was replaced with a demand for toy forges.