Battle Mode

Battle Mode is an option in both Golden Sun games. It is where players can battle and practice different strategies against monsters and bosses from the game and against friends with use of a link cable. No coins or EXP are earned in Battle Mode. With this mode you can use all the items and Djinn that you currently have in your posession.

Lobby
In the Lobby you can talk to all the Adepts you currently have in your party. Other than that there are just a bunch of NPC's you can talk to. But if you talk the lady in the lower left while holding a shoulder button in The Lost Age you can listen to the game's Sound Test option.

Monster Battle
The Monster Battle mode is initiated when you have no link cable inserted into the console. With it you can battle any monster you have already battled in the game including boss battles. Basically put, it's the only place where Isaac can square off against Poseidon.

Link Battle
With the Link Battle option you battle a friend with a copy of the same game to see who's better. Though with this mode you cannot link the original Golden Sun to The Lost Age.