A plant-covered rock monster that wore an orange loincloth. He can manipulate soil, split into rocks, and launch the rocks on his body. Boulder Beetle's heart had the power to emit Negative Proton Rays and can even allow him to regenerate. Nefaria wanted Boulder Beetle to use his Negative Proton Rays on Dex making the mission easier for Dregon. She set a trap for Dex by causing an explosion in Leawood Canyon. When Dex finds the hole, he is pulled under by Boulder Beetle and is grabbed the hands on the walls. Dex breaks free and transforms into Masked Rider. Dex broke free from the arms on the walls by turning into Super Blue. But after escaping from underground, Dex's Super Blue powers turned off. Dex eventually escaped on Combat Chopper. Later, Dex was given a recharge from Magno, Chopper