Fuchin Falls Cave

Fuchin Falls Cave is a dungeon-style location in Golden Sun, which is connected to Fuchin Temple on the east end of the continent Angara. It is blocked by a man by order of the temple's head monk, Master Nyunpa, and it is a test of Psynergy powers, which Nyunpa teaches as "Ki" spiritual power. Nyunpa will grant Adepts with Psynergy access into the cave. The cave itself includes puzzles involving rolling logs and using a key item called the Dragon's Eye on a dragon statue to light up a room and reveal the shadows of an otherwise invisible path. Its treasures are the Jupiter Djinni Zephyr, the Arctic Blade, and the utility Psynergy item, the Orb of Force.

This is actually an optional dungeon that can be skipped, and the Orb of Force is not required to reach the game's end. The Orb of Force is required to get to some major secrets both in this game and in Golden Sun: The Lost Age, however.

Walkthrough
When you enter through the waterfall, you are presented with two logs floating in the water to step on, and when you press up towards the water, you ride the rolling log to the other side. Do this to with the log on the right to reach a chest that reveals itself to be a Mimic, and defeat it to get a Game Ticket. Roll the log to the left up to enter the next area, where there are many wooden stumps in the water serving as platforms; hop up, left, go up one sace, hop right, hop up twice, hop right, hop up, hop left, bypass the top door, and hop to the stairwell at the left part of the room. Let the subsequent path lead you to a dark room, and go down the stairs to the left.

In the next room, rather than ride the horizontal log below you south, go along the right side of the room and ride the right vertical log left to reach a chest containing the Arctic Blade weapon, then ride back and ride the top log down. Enter the next room south to a room with spikes on the floor; while the idea is to avoid them, in this case it realistically makes no difference whether you walk straight over them or not, for they only hurt all Adepts for a single hit point at a time, so simply walk right and down through the spiked path to reach the room's exit quickly. Back at the first area of the dungeon, ride the horizontal log right and enter the door at the right end.

In the room that has a square-shaped area of spikes in front of you, go below them to see a Jupiter Djinni off to the right. It is reached by riding the horizontal log down, riding the vertical log left, riding the horizontal log back up, hopping left and down, and riding the vertical log right, and once you defeat it in battle you earn the Jupiter Djinni Zephyr. Then ride the bottommost vertical log all the way up to the doorway at the top of the room beyond the spikes.

In the next room which has two horizontal logs parallel to each other in the water, ride the upper horizontal log up, then ride the upper right vertical log left, hop up, and ride the lower horizontal log up, and hop left to go down the stairs. You find the Dragon's Eye jewel, a key item to make use of in this dungeon. Go back upstairs and go up the stairwell at the upper end of the room with the rolling logs, and follow the path to the dragon statue in the dark room. Use the Dragon's Eye on it to light up the room, and you'll see that there is the shadow of a pathway being cast down on the ground below by what is, in actuality, an invisible pathway that connects to upper right exit.

To save time, cast Retreat to get to the dungeon entrance, exit Fuchin Falls Cave, and reenter it to reset the logs in the dungeon, and now go through the dungeon again up to the point before you went down the stairs to the room with the Arctic Blade; now, you can walk on the invisible pathway indicated by the shadows on the ground below. (As a matter of fact, this pathway could be traversed even while the room was dark.) Follow the path beyond that and enter a room where the dungeon's main treasure, the Orb of Force that bestows the Force Psynergy, lies in a chest next to a stone tablet. Once you've collected that, you can safely cast Retreat again and leave the dungeon.

Items
Arctic Blade - In a chest in the second room. Dragon's Eye - In a chest in a room after solving a log-rolling puzzle. Use it on the dragon statue in the dark room to light the room up and reveal the "invisible" path. Orb of Force - At the end of the invisible path.

Djinn
Zephyr - In a log-rolling puzzle south of a large mass of spikes.