Koga Takuza is an unseen antagonist in the TV show; Teenage Mutant Ninja Turtles. Koga was mentioned in the episode "The Legend of the Kuro Kabuto". He was both the founder, and the original leader of the Foot Clan, as well as the creator of the Kuro Kabuto (more commonly known as the Shredder's helmet).
According to the Shredder, Koga Takuza was a feared and powerful swordsman. He was capable of easily defeating every samurai he encountered with only his katana. Every time he killed his opponent, he would take their a piece of their armor as a token. After taking a certain amount of tokens, Koga then forged them together with an indestructible alloy that was said to be harder than steel. The helmet was then titled the Kuro Kabuto. After which, Koga created the Foot Clan. Koga would also wear the helmet to both let people know he's the leader of the Foot Clan, and to strike fear towards everyone he encounters.
Before he died, Koga gave the new leader of the Foot Clan the Kuro Kabuto. Every time someone was appointed the new leader of the Foot Clan, the previous leader would give the helmet. This tradition was held all the way to Oroku Saki, AKA the Shredder, who is the current leader of the Foot Clan.