Wishing wells have a metabolism which is much like that of pitcher plants. Coins cast into their bowels are digested over the course of several decades, and are eventually left faceless and without luster. The pit then excretes a perfume of willpower into the atmosphere, resulting in subtle shifts in the ways of the world.
Most who throw coins into their mouths of stone are disappointed to find that their wishes do not come true. This is most often due to extreme impatience; humans desire love, wealth, power, and goods relevant to their immediate needs, rather than the kind of things experienced on a stone structure’s timescale. Such prayers become impossible long before they can actually come true.
Even so, these wells are extraordinarily potent when used correctly. Those who exploit their unique biological properties use them to prevent the spread of plagues, bend the course of rivers, and change the climate of their homelands. Instead of sudden shifts in the lives of those who use them, they bring gradual changes that permeate the landscape beneath their feet.
The power of any one well is limited, however, and can be exhausted. If fed too many coins, the pit’s hunger can be accidentally satiated, causing it to cease functioning for several centuries. Once this period has passed and it’s ready for more, it lets the world know by letting out a great and terrible belch.