500 years before the series, Oroku Saki was the leader of the peaceful Foot Clan and father of the Hamato Clan founder, Karai, whose soul was swallowed by the demonic and nigh-unstoppable Kuroi Yōroi armor after it was forged by a horrible Oni (that resembled Krang). After being reborn as the Shredder, Saki led the Foot down a path of villainy, conquering many villages and destroying many innocent lives in the process. With no other choice, Karai was forced to create her own clan, the Hamato Clan, to combat the tyranny of the demon. Shredder terrorized Japan until he was defeated by the Hamato Clan, due to Karai using her mystic Hamato Ninpō energy (since no mortal weapon could harm Shredder) to send Shredder into a dimension called the Twilight Realm, and the Kuroi Yōroi was scattered across the world to prevent his return. The side effect of Shredder's defeat had sent Karai into the Twilight Realm, along with Shredder's sapience being sealed away. In the aftermath, Karai's remaining followers made it their sworn duty to watch over the armor pieces and to never allow the Foot to reclaim them.