That or a series of humour events that lead to them trying to knock the stuffing out of one another :P
Same in some respects for those Celestial Mages who have Golden Keys. As we've seen in the anime/manga, all twelve Spirits together in one place are quite formidable, and as we've also seen, they tend to have relationships and chat to one another in the Spirit World.
Trying to imagine the scenario that would bring together all the Golden Key bearers together in one place...
Just random musings here. Thoughts or ideas are welcome :3