The Trial Series are artificial monsters created by BOARD, combining human and Undead DNA with machinery. They cannot be sealed with Proper Blanks; in fact, Blanks are absorbed, allowing them to recover quickly. The Trials were developed to interfere with the Undead Battle Fight. In early production sketches, they were referred as "Undeadloids."
An Electric-Type Undead disguised as Shiori's father, Yoshito. Originally, his program was to protect Shiori by her father because he was dying. Before he died, he transferred all his memories to the Trial. He is reprogrammed by Tennoji to continue to monitor the fixed Undead battle and remove potential threats. He dies saving Shiori from Trial G after remembering his original programming.
A Capture-Type Undead sent after Kenzaki, who is one card away from attaining King Form. Trial D was destroyed by Blade's King Form.
A Shooting-Type Undead based on Garren's data & DNA. Destroyed by Blade King Form's Royal Straight Flush. Another appeared in the Hyper Video Special Blade vs. Blade, disguised as Kenzaki wearing a red scarf, it copied the Blay Buckle and transformed into Kamen Rider Blade. He fought the real Blade to a standstill with the clueless Tachibana and Mutsuki unable to tell the obvious difference. He was eventually defeated by Blade's Jack and King Form with the help of Leangle's Remote Tapir and Garren's Gemini Zebra.
An Energy-Type Undead used to capture Kenzaki that was destroyed by Wild Chalice's Wild Cyclone.. Evolution Paradoxa (Category King of Hearts) Undead's DNA is used.
A Fighting-Type Undead which was based on Leangle's Rider data; he managed to defeat Hikaru Jo/Tiger Undead and fought off all four Riders. It was about to kill Shiori until Trial B intervened remembering the original programming his creator gave him. Destroyed by Wild Chalice's Wild Cyclone and Blade King Form's Royal Straight Flush.