Occasionally mistaken as stars and common in the Land of Wind and Shade, fireflies have no real purpose so far. The ones generated by Sburb have a very large or indefinite lifespan and don't need to eat, even surviving inside amber.
These fireflies are stuck in the sky when the breeze stops flowing from the pipes on LOWAS. It was stated by an amphibious inhabitant that the fireflies are stuck because of a spell cast on them by The Slumbering One.
Furthermore, there were at least 4 fireflies in LOCAH as it is shown that the four lanterns that power the crypt mechanisms were These seem to be connected to the vital state of each the post-scratch kids. Dirk's firefly apparently shatters the lantern it was encased when Dirk gets revived, and the building when the kids simultaneously reach the god tiers.