Idearium is the raw, blue ore harvested from the Idea mines and run by Idea Master (Also called IM for short).
It is processed into raw ideas that are distributed throughout the night by the Idea fairies.
...Okay, so there are no fairies.
Instead, when there is a glut on the market for raw Ideas, IM puts it into the city food and water supply so that the prices go up and so that, as a secondary effect, people get more ideas for their stories and make new chapters.
This keeps everybody happy, to an extent.
- Idearium is also made into the newly minted Fables, though that is now only used out of tradition. The City Council has just released plans to make the Fables completely out of metal or paper, thus making them worth their value, as such materials are rarely found in the city. Thus the prices for Ideas will fall, and the cycle will begin again.