If you played the first Golden Sun, this place should be familiar. Go up the stairs until you reach the top. Another villager will block your way. Finish him like you did with the other one. Enter the next screen and climb down the vine. Try to go into the cave, but 3 villagers will appear. Don't worry though, you can take them no problem.

Walk inside the cave. Go down the stairs and through the staircase. Here, you can get a Psynergy Stone, but when you try to approache it, a monster will attack you! No worries here, though, since you can kill it with ease. Take the Psynergy Stone and save your game. After you leave the cave, get ready for a long cinematic.

The ground starts shaking hard and Idejima splits apart from the continent. Then, the following sequence is the ending scene you've seen from the original Golden Sun. The sequence ends with Kraden's last question: "What does it mean, Alex?"