Fluorescent Alcoholic Fungus, also known as FAF, is a special kind of neural-sentient fungus, commonly found in non-hygienic taverns..
The good: You don't need light. They are very beautiful and provide a special ambience in the room.
The bad: The noise. The noise!
The PCs encounter a strange set of artistic drawings done on the ground as they pass through a city. It has been done in chalks and no one saw who did it. Wizards might recognize the writing within the colored square as an obscure and dead language with a message stating that a prominent wizard and a retired bard have discovered how to populate Arcadia with the spirits of the dead!
Is it a local hoax, or are the PCs crossing the path of a very deranged and possibly dangerous mage?