Izumo Ruins

The Izumo Ruins are an underground, cavernous area underneath the town of Izumo that functions as an optional dungeon in Golden Sun: The Lost Age. The entrance is well-hidden in the ring of pillars in the upper right area of the town; you must Move the leftmost pillar right one space so it is properly aligned with the others, then cast Reveal to see and enter the hole that has now opened up in the ground.

Once inside the dungeon, you will need the Parch Psynergy won in Aqua Rock and the Sand Psynergy won in the nearby Gaia Rock in order to properly explore and fully loot the cave. The main discovery within the cave is the Ulysses Summon Tablet at the end.

Walkthrough
Use Frost on the puddle, then use Sand to get on the other side of the Pound pillars (if you use Pound, you can't continue). Freeze this puddle, then use Sand to get back to the other side, climb the ladder, and jump across to the door.

In the next room, go right and down the ladder. Pound the pillar, then use Sand to get on the other side of the rocks. Go up to the pillar behind the rocks and Move it right one space. Go back to the entrance of this room and take the left path. Use the pillar to jump across, then go down the ladders.

Go up the right-hand ladder down here, and go all the way around, using the Pound pillars to get the Phantasmal Mail from the chest. Go back around, and now you can Pound one of the pillars to get past. Go up the left-most ladder and use Parch on the water. Go down the ladder and through the new door. At the end of the tunnel, you can get the Ulysseys summon from the combo tablet! Ulysses requires 2 Mars and 2 Mercury Djinn to summon, and it has an added effect of sometimes immobilising your opponent for a turn! Use Retreat and exit back into Izumo. Use whatever you need to, then leave.

Collectibles
Ulysses: The reward at the end of this dungeon, a Mars-based summon sequence.

Phantasmal Mail: In a chest reached by hopping across two log pillars that you must then pound afterward to continue forward.