The Walls that Never Fall

The city of Greenfall has been around for more then 3000 years becomes of this there is many stories that have passed down though the centuries. Most of these come from the ancient times of the city before the monarchy. This particular belief is fairly new in the span of the city, origination sometime between 1200 and 1600. 
According to this belief the Obsidian stones that are found in the mountains of the region, have protective powers. When they are imbedded into the walls of buildings that wall can never fall down. 
This rumor started to spread after the monarchy started to use these stones in the government buildings and after a few hundred years nothing bad had happened to the city. This was in stark contrast to the few hundreds years prior to 1000 when the stones were first started to be used, where the city had been at wars, destroyed by the Great Trembling, having plagues, and then almost fell again in a civil conflict. Of corse this was mostly to do with the Shadow Writers having gained a strong foot hold in the government by this time not because of the stones. Even so this myth continues. 
As this myth became popular more and more people started to put these things in their homes in a hopes that they will protect them. And perhaps it had worked as there has been no great problems in the city since the practice has become common. Then again there has not anywhere in the world after the Shadow Writers took over so it is hard to say.