The Cave-Door Key is a Quest item left behind by Briggs in his room in Champa. It is a small golden key found in Champa's cave lodgings, on the right side of the third floor of the tunnel leading up to Obaba. It is used to unlock a door in a cave across the water underneath Champa. In the room is a total of 102 coins. There is also a pillar burning. Move the pillar into the hole then cast Thermal. This will lead to the real treasure, Orihalcon.