The Golden Hammer is a Key Item in Chrono Trigger.
to obtain the Golden Hammer, go to the lost sanctum. The hammer is obtained through a quest from a Reptite. You must defeat a Golden Ogan to obtain the Golden Hammer. The Golden Ogan is found not far from the area it ran from. You have a choice to hand the Golden Hammer to the Reptite, or you can refuse. Giving it to the Reptite will net you 100,000 Gold.