After losing the power of the "Stone of Heaven" within him, he becomes the Grand Mutant Darom, a trilobite-like creature. In this form, he can discharge laser beams from his fingers and use his feelers like ropes. Following Baraom and Bishium's death, Darom attacked the ex-Shonen Warriors until Kotaro arrives and transforms into Kamen Rider BLACK and fights Darom until Shadow Moon arrives.
After Shadow Moon defeated Kamen Rider BLACK, Darom is sent alongside Bat Mutant to find Kamen Rider BLACK's body. Darom finds Whale Mutant's cave and finds out that he's been revived by the revival ceremony done by Whale Mutant's tribe. Darom and Bat Mutant then had some Gorgom worshipers capture Whale Mutant as bait for Kamen Rider BLACK.
After Kamen Rider BLACK threw himself in front of Whale Mutant, he then used his King Stone Flash to deflect Darom's attack before killing him with the Rider Kick.
Let's Go Kamen Riders
High Priest Darom, the leader of Gorgom's High Priests and the Gorgom member chosen to represent the group in the Shocker meetings. He actually has little interest in the alliance, and despises Shocker's interest in ruling over humanity, wishing to just eliminate the entire species. However, he's eventually convinced to continue with the alliance for some time. When the timeline is partially restored and the Riders return, he briefly engages Kamen Riders Black and Black RX in combat, only to escape. He's destroyed when Great Leader became Rock Great Leader.