A robotic monster that can manipulate fire. Double Face and Fact had created a chemical that when mixed with water will form a toxic mist that takes over the minds of whoever breathes it. In the event that Dex traces the toxic mist to the factory, Double Face prepared Fire Bug to fight him. When the Stewarts were at the community pool for the day, everyone but Dex got affected. Dex transformed into Masked Rider and used Magno to trace the mist back to the source. Dex engaged Fire Bug at the factory. Fire Bug dragged Dex into a room where it started a fire. Dex transformed into his Super Gold form making him immune to the heat. After breaking out of the room, Dex destroyed Fire Bug with his Ecto-Ray and stopped the gas flow. Fits the theme of Cycloptor's monsters.