The Legend of Zelda: Oracle of Ages can be linked with The Legend of Zelda: Oracle of Seasons using a password system. Playing a 'Linked Game' unlocks exclusive content, including new characters, powerful items, and an extended ending that reveals the true antagonist behind the events of both games. To start a linked game, you must first complete one of the Oracle games and receive a 'Secret' password.
When starting the other game, choose the 'Secret' option and input the password. This will carry over certain aspects of your completed game, such as your name and some items, and introduce new events and characters. The most significant reward is the ability to obtain the Master Sword and the Red Ring or Blue Ring, depending on which game you started as the 'linked' game. It also unlocks the true final boss battle against Twinrova and Ganon.