A wisp.
Wisps are wasp-like etheric creatures with the ability to create illusions. Wisps make their nests out of paper and wood.
Antimony encountered a Wisp in Chapter 44: Crash Course, during which it claimed to be the Seed Bismuth and tried to trick Annie into bringing it to the court. An entire nest of Wisps later appeared in the court after Loup destroyed the Annan Waters.