Inverse Fiends

The "Inverse Fiends" refers to a group of 8 Buddyfighters formed by Gratos to counter the Great 8 Omni Lords and their attempt to seal Yamigedo.

History
The first two members of the group, Sofia and Shido, were recruited and served under Ikazuchi at the beginning of Future Card Buddyfight Hundred. For the majority of the season, they performed various acts under Ikazuchi's order in order to satisfy both his and Yamigedo's hunger.

After a series of events, such as Gratos's appearance, Noburu's kidnapping, and Ikazuchi's loss to Gao and disappearance, Gratos took over the role of Leader of the Hundred Demons and began to put into motion Yamigedo's revival. He began by using "Knight" to defeat prominent Buddyfighters in the area of Cho Tokyo and, should their skills impress them, they would be kidnapped, brainwashed and turned to stone until they were needed.

Davide Yamazaki was recruited as a result of a chance reunion between him and Shido. After finding out Kiri's true origins and his subsequent loss towards him, he decided to offer his services for a chance at revenge.

In H Episode 37, all of the members were used for their intended purpose and with their powers combined, managed to thwart the Omni Lord's Sealing Ritual. With that, Yamigedo was able to successfully metemorphised into his most powerful form yet.

Trivia

 * It is unknown if Ikazuchi was a possible candidate for the Inverse Fiends, given he was brainwashed by Gratos as well.