I think that the King of the Underworld Mard Geer and the Celestial Spirit King fight more than 1 fights because in episode 249 Mard Geer said to the Celestial Spirit King "I don't believe I will lose to you this time, either."
but it's impossible for Mard Geer to go to the Celestial World, so I believe that a golden key or more was destroyed before Aquarius.
Are there more than 12 golden keys?