Biorider is the seventeenth episode of Kamen Rider Black RX. It's the fourth and final part of a four-episode Strange Demon World story arc. It features the debut appearance of RX's second alternate form, Biorider, following Roborider which first appeared two episodes previously. Biorider's debut is accompanied by the introduction of its corresponding Acrobatter form, Macjabber. The Sahara Kids also learn that Kohtaro is RX in this episode.

With Hitomi fully transformed into Princess Garonia, Kohtaro has to figure out a way to finally resurrect her memories and save her before he, Shigeru and Joe the Haze are executed by Maribaron's pawn.