|This article is about a/an kaijin in Kamen Rider Black RX.|
A one-eyed alien monster with an elephant-like trunk for a mouth. It can shoot a beam from its eye, and spew steam from its trunk. It disguised itself as a masked Sportsman named Great Mask and brainwashed kids into rooting for him, including Shigeru and his friends. When fighting in a re-match against his latest boxing opponent, it turned out that Bio Rider had merged with Balunbolun's opponent and so he shed his disguise. As the boxer got everyone out of the building, Bio Rider fought Balunbolun who made off with a small boy. After turning into water and catching up to Balunbolun, Bio Rider reverted to Kamen Rider Black RX and fought him. Acrobatter tackled Balunbolun freeing the boy. RX then used his RX Kick on Balunbolun before destroying him with his Revolcane.