Disappointed by Shocker's numerous failures to defeat Kamen Riders Ichigo and Nigo, the Great Leader of Shocker decided to completely rebuild Shocker. Without the knowledge of even the other Shocker leader, the Great Leader secretly met with General Black, an executive of the mysterious Geldam organization from America, to discuss the merging of their two organizations. They eventually finalized their plans and put the merger into action after the death of Ambassador Hell.
The Great Leader took over Geldam and converged it into Shocker, combining their resources. Deeming most of the remaining members of Shocker to be unfit to join the new group, Great Leader of Gel-Shocker ordered the deaths of nearly all of the lower members of Shocker. The Great Leader had all former Shocker personnel purged, blowing up various remaining Shocker secret bases worldwide and having all of the Shocker Combatmen liquidated and replaced with Gel-Shocker Combatmen. Black sent the Geldam kaijin Ganikomol to exterminate the remainder of the Shocker Combatmen so they could be replaced with stronger Gel-Shocker Combatmen. Ganikomol was later encountered and defeated by Kamen Rider 1. Although Rider 1 destroyed Ganikomol he was unable to prevent the merger of Shocker and Geldam.
Rising from ashes of Shocker came Gel-Shocker. Despite being led by the Great Leader of Shocker, the majority of the organization's resources were provided by Geldam, with the Shocker Riders being the only visible carryover from Shocker.
After the death of General Black and the Double Riders' final battle against the Great Leader, Gel-Shocker was ultimately destroyed.
Despite Gel-Shocker's fall, many members of it survived and would go on to form the Destron secret society to carry on Shocker's legacy and goals of global dominion.