Swarm of Hoard Scarabs

Swarm of Hoard Scarabs
Hoard scarabs are beetle-like creatures that, through some feat of natural adaptation or alchemical ingenuity, blend in perfectly among piles of gold coins. They feed on tiny mites that infest a dragon's scales and lair, and their painful bite can be a strong deterrent to would-be treasure thieves.
Hoard scarabs also produce a glittering metallic dust from their wings that coats intruders who get too close to them. The magic of this dust allows the lair's draconic owner to sense intruders' location as they move about the lair.