A one-horned bluish imp monster armed with a pitchfork. He can shoot a beam from its horn. Maribaron planted him inside Kohtaro to kill him when he was being pursued by the police. This was a plan by Maribaron to hack into the city records and make specific people look like criminals. When Kohtaro found out about Wilki while he was in jail, he transformed into Kamen Rider Black RX and escaped from his cell. Wilki even poked him while he was escaping on Acrobatter. While in the sewers, Kamen Rider Black RX became Bio Rider and found out what the Crisis Empire was up to. When the next person was arrested, Wilki attacked Kamen Rider Black RX and attempted to deliver the final blow. Kamen Rider Black RX faked his death and was brought to Maribaron. He eventually became Bio Rider right as Marib