Calm (Final Fantasy X)

In Final Fantasy X, the Calm is the ten years of peace that follow when a summoner defeats Sin, dying and posthumously becoming a High Summoner in doing so. Sin would inevitably return a decade later however, at which point summoners would defeat Sin again, repeating the process ad nauseum. The Eternal Calm came when a summoner named Yuna was able to defeat Sin for good, bringing peace to Spira.