The Ninja Monster Clan were a group of super villains committing crimes in The Seventh Samurai's hometown of Shogun City. The Seventh Samurai had defeated them, making Shogun City a safer place, but Manny Rivera hired them to throw a fight with Toshiro, not realizing who they were.
They appear as four-armed creatures with striped horns, devil tails, and metal claws. They wear black Ninja uniforms with spiked shoulder pads that have skulls attached to the ends. All of them, except for their unnamed leader wear veils over their faces.