the gunster is the main antagonist in the fan fiction story Gunslingers of Metru Nui. it includes locations from the cannon but this article is not cannon.
gunster was originaly a weapon scientist called revolvic. he invented the first guns used by bionicles (revolvers) before being driven mad by the surge of lust for power his inventions gave him. he made two types of gun. the rifle like that he unveiled to the toa metro and that the matauran began using. and the revolving cylinder based weapons that he and some followers removed their hands and attached the gun instead. when toa lhikan came to stop him he shot lhikan and declared his name to be Gunster.