Izumo Ruins

The Izumo Ruins (イズモの地下遺跡, Izumo's Underground ruin) 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.

Lorewise, this is merely a secretive area underneath Izumo that is a place that only Adepts are able to gain access to, because the hidden entrance can only be entered after the circular series of large pillars of earth and stone surrounding it have been realigned, and only Adepts with the Psynergy power of Move can perform that. The ruins and the stones around their entrance are described as having been around "for ages", and no one knows who originally put the stones there. Lady Uzume of Izumo, for whatever reason, has one townsperson keep a constant guard over the misaligned stones.

Walkthrough
Climb down the ladder from the outside, and cast Frost on the right puddle to turn it into an ice pillar. Then, stand on the beige sandy part of the floor above the wooden pillars, and cast the Sand Psynergy acquired in Gaia Rock to turn yourself into a lump of sand that can move along the surface of the sandy ground and underneath the right wood pillar. Resurface below the wood pillar and cast Frost on the other puddle, then Sand-travel back north and resurface above the right wood pillar. Now you can climb up the right ladder and hop left across the four pillars, and enter the doorway to the upper left.

In the next screen, go up until you find a fork in the road, go right, and climb down the ladder at the lower right part of the screen. Go up to a wooden pillar, and cast the Pound Psynergy to flatten it, and then Sand-travel past the rocks above it. Go to the upper-central part of the area where there is an earth pillar bordering a ledge to the left, and use Move to move it one tile right. Return down to the fork in the road, and take the left fork, which linearly leads you along the room's perimeter clockwise and across the earth pillar you moved. Climb down the ladder in the hole leading into the floor below.

After climbing down the long ladder from the floor above, immediately climb up the ladder to the right, and this linearly leads you on a counterclockwise trip to the chest on the lower right part of the screen, hopping across two wood pillars to do so. The chest contains the artifact body armor Phantasmal Mail. Return to the two ladders and go down, and pound your way past the two wood pillars. Follow the room's lower perimeter west until you come across two more ladders separated widely apart, and climb up the leftmost ladder. You are lead to a pool of water that is removable with the Parch Psynergy found in Aqua Rock. Climb down the ladder into the newly open part of the room and enter the new cave entrance to find the final room, which is a hallway where you get to collect the Ulysses summon tablet, the dungeon's ultimate reward. Cast Retreat afterward.

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.