"The Evil King Ganon defeated"
In order to acquire this Magic Ring, Link needs to defeat Ganon in a Linked Game of Oracle of Seasons or Oracle of Ages. It does not matter which game is completed first. After defeating Ganon, Link will be given the Hero's Secret, which can then be used on either game. Upon starting the game, Link begins his quest with the Victory Ring.
When worn, the Victory Ring has no effect at all. The purpose of this ring is simply to recognize that Link has defeated Ganon.