Gaia Rock

Gaia Rock (known to the locals as Mt. Mikage) is a mandatory dungeon in Golden Sun: The Lost Age. It is one of the four Elemental Rocks scattered across Weyard, and one of the few locations visitable in Weyard's would-be northern hemisphere in TLA. Gaia Rock is east of Izumo and is home to the Serpent that has terrorized it's people. Gaia Rock is the elemental rock of Earth and as such the Psynergy found in the dungeon is Sand. It differs with the three other Elemental Rocks quite a bit in how it is traversed and that it is the only one that holds a boss fight at the end. Gaia Rock is also more relevant to the overall plot of TLA as it is entwined with the people of Izumo. It is probably based off of Mt. Fuji.

Walkthrough
Gaia Rock Exterior

Approach the rock, but don't go inside. The only way you can go will end in tears if you attempt it now, so instead go to the left-hand side and climb the wall. Shove the pillar off, then climb around and move it onto its metal plate. Go all the way to the right, climb down the other ladder, then go back across to the left wall, and climb up. You can use the pillar to hop across and use the next wall to climb up to the next area.

This bit gets quite confusing. Go up the right-hand wall, and scale it as far as you can (you will need to use the partially-swinging thick green vines). Up here, use the next vine to climb down and grab a Nut from the chest if you want to. Use the groove here to slide down (you'll be at the top of where the left-hand climbable wall would have taken you). Climb up the wall above you, then head left. The whirlwind statue here will give you a hint on what you need to do with the vines - using Whirlwind will blow them around so you can use them to swing across gaps.

Go down the wall (not all the way) and try this out to cross to the other side of the vine. Move the pillar one space to the left, then go back across the vine and down. Climb up, push the pillar onto the metal plate, and continue scaling up the cliff. Exit the area to the left.

The next area is deceptive too; the vines will make you think there are tons of different paths. You'll actually find there is only one, with one or two obvious dead-ends. You'll eventually reach a wall you can scale to the next area.

This is where Gaia Rock gets even more annoying. The wall has many different ways of climbing it, but going certain ways will cause moai heads to emerge from the wall and shove you off, making you start again from the bottom of this area. Keep to the right for the first section (once the statues at the bottom go out of view). Hug the right-hand side again for the next part. When you get to another junction, go left, and climb STRAIGHT upwards. If you're a little bit too far to the right you'll run into a moai head that'll knock you off. After a short climb you'll clamber up to flat ground again. You're at the summit now, so just follow the path weaving between the rocks and leave this area to the right.

Don't move the pillar here - go to it and hop across. You can grab an Apple from the chest over here. Now go back, move the pillar all the way to the bottom of its groove, then jump across it. Follow the long, winding path until you reach the very top. The altar here appears to be the only thing here, but you'll recognise the Reveal symbol. Use Reveal and grab the weird Dancing Idol from the altar. Now, Retreat back to the base of Gaia Rock. Now you can go inside.

Gaia Rock Interior

Before, straight ahead is the only way you could go. That leaded to an endless maze and, past that, an undefeatable boss that recovered all its HP at the end of every turn.

But now, you can use the Dancing Idol on the familiar altar here, and the two sinister statues on either side will move out the way, allowing you past. Take the right-hand door.

Follow the long path here until you reach a patch of weeds. Use Cyclone here and a load of floating grassy platforms will appear, which will allow you to take the other door at the entrance of Gaia Rock (make sure you use Cyclone on all of the weeds). Now, either follow the path all the way back to the entrance or use Retreat and re-enter Gaia Rock. Once you're there, take the left-hand door. At the end of the path, you can use the floating grass platforms to get across to the door at the top of the room.

At the end of the path, you'll see a large room. Ignore the steps on the right-hand side for the mean time, and go left. Follow the path until you reach the next room. Use Cyclone on the weeds in here to uncover a Mad Plant. This relinquishes a Potion when you beat it. Ignore the long climbing wall to the right here, and go down the steps and through the door at the bottom.

The weeds around the altar don't hide anything, so go ahead and use the Dancing Idol. The statue will move, but let light through to the hole. This light ray will be reflected by a purple orb in the Serpent's lair, weakening it slightly. Now, if you were to go and fight it, you'd still lose. You need to get the other three beams of light on the Serpent.

Head back to the room with the long wall, and start shimmying across it. Go along the bottom first, then top, then hug the bottom of the climbable section around to the platform. Use Whirlwind and swing across using the vine, then decend the steps and go through the door. Don't use the groove in here, instead use Cyclone on any of the weeds to drop the altar down a floor. Now you can use the groove.

You could have got two other beams of light down here before, but it's quicker to get the altar down first and get the other three light rays all at once. Use the Dancing Idol on the two altars and Cyclone on the weeds. With all four beams of light blasting the Serpent, you've now knocked his regeneration rate down from a ridiculous amount to 30HP a turn. That's right - even being weakened this much it still regenerates.

Retreat to the entrance of Gaia Rock again, and this time you can take the middle path. You have to solve a relatively simple Move puzzle along the way, and once you're past you can head through the door.

Now it gets tricky. You're in the endless maze section. Don't even think about moving until you've switched one Venus Djinni with one Mars Djinni on Felix and Jenna. Set Growth to a Psynergy Shortcut next. Ordinarily it would take you ages and ages to navigate this maze, but Growth makes the plant in the middle tell you exactly where to go.

The way to go is:

Left, Up, fight Mimic for Game Ticket, Up, Right, Up, Right, Right, Down, get Rusty Mace from the chest, Right, Right, Up, Right, Right, Up (see how hard this would have been without Growth?).

You'll trigger a scene, where Susa's attacking the Serpent. Nothing works, and then he gets blown off his feet by a fireball. Save, put all Djinni back to their respective characters, and Standby 4 Venus, Jupiter and Mercury Djinni, and 3 Mars. The best configuration is Flower, Cannon, Spark, Blitz, and Shade were the only Djinni set (these are the most useful Djinni).

Now approach the Serpent and interact with it to start the battle.

Collectibles
Exterior:

Apple: Found in a chest near the area where you can find the Dancing Idol. Dancing Idol: At the peak of the exterior, there is an empty pedestal surrounded by a ring of log pillars. Cast Reveal to see a dancing figure, which you can obtain as an item. Use it on any similar-looking pedestals in the interior portion to make progress in the interior of Gaia Rock. Nut: Found in a chest in the first screen off the ground level screen.

Interior:

Sand: This Psynergy is the reward that presents itself following the boss fight with the Serpent. Inspect the stone slab that emerges out of the ground.

Cloud Brand: Right after getting the Sand Psynergy after the boss battle, immediately cast it to transport yourself to the end of the trail of fluid, then inspect the end of the stream with the A button. Rusty Mace: Found in the chest later on in the winding multi-room path towards the most interior room.