The Ancient Circuit is a Boss Key in Skyward Sword. Like the other keys in the game, it is used to open the doorway into the Boss's room by twisting it around until its shape matches the lock and can be pushed in, which opens the door. In the Lanayru Mining Facility, where the Ancient Circuit is found, the boss is Moldarach. In order to obtain the Ancient Circuit, Link must defeat two Armos using the Gust Bellows, which opens a gate that previously enclosed the treasure chest holding the circuit. The key is made of gold, similar to the Golden Carving and Dragon Sculpture, and inlaid with circuitry.