Within the Hero's Tower, at the start of each battle, there would be an invisible phase of the moon in the background, which included six different phases: new moon, waxing crescent, waning crescent, first quarter, gibbous, and full moon.
These six moon phases didn't appear randomly but in a fixed sequence, which meant that you would only encounter a full moon once every six battles!
This was also why many disliked the Moon Emblem: the Moon Hero's Divine Arts required a full moon to be effective or to exert their maximum power.
This meant that in every six battles, only the one during the full moon would see an exceptional performance from the Moon Hero, while the other times, they would be quite ordinary, or even a liability.