Golden Sun: The Lost Age/Mikasalla

Mikasalla is a pretty dull place, it has to be said. Climb up the ladder to the first level of the watch-tower-thing, then jump to the ledge on the right. Follow it north to a chest, which has 82...count them...82 coins in it. Also in the southwest corner of town there is a box a sheep runs into containing a nut. You can't get the Mars Djinni here yet, so rest using the Inn. Be sure to check the barrel in the corner, as there is a Lucky Pepper. The chances are you don't have enough money to afford any of the stuff at the equipment shop here. Once you've finished with Air's Rock, Yampi Desert and Alhafra though, you will. When you're done, exit Mikasalla, and head northeast. There's a mountain which you should head around, near a dark green patch of grass.

Sour, the Mercury Djinni
Nearby, next to the mountain, there is a small triangular forest. Wander around in here until Sour appears in a random battle. Use Mars and Jenna's fire Psynergy to take it down whilst Felix and Sheba help. If it runs, keep wandering around here until it reappears. When you defeat it, it'll join you. Head back to Mikasalla, rest, then head directly east this time.

When the path deviates, a little, head south across a bridge. Head around here and across another bridge, until you reach another fork. On your left is Garoh, which you can visit for a cutscene, as well as an Inn and Sanctum. Just shove pillars around using Move to scale the cliff to get to it. Otherwise, head right at the fork, and you'll reach a river with a bridge leading to a wide desert. Go left into the desert and approach the pink rock in the middle.