Otka Island

Otka Island is a visitable location in Golden Sun: Dark Dawn.

Otka Island is an island with a metallic labyrinth within a cave, hidden away amidst reefs in the middle of the Otka Sea, between Port Rago of the Morgal Region of Angara and the Nihan Islands, where Izumo was in The Lost Age and where Yamata City is in Dark Dawn.

The only way to reach Otka Island is to allow the whirlwind blowing around the Otka Sea to carry your ship to the Island. Getting back aboard the ship and sailing within the reefs around the island causes the whirlwind to come back and drop the ship somewhere north of Tonfon's port. The two things of note in the Otka Island dungeon are the Jupiter Djinn Lull and the summon Catastrophe, guarded by an Ancient Devil in the depths of the labyrinth.

First Visit
The Jupiter Djinni, Lull, is at the very beginning of this Dungeon and to get to it you need Himi as well otherwise you cannot get the Djinn nor Catastrophe because you need her Search Psynergy. Also of note you can not get Catastrophe without the Sol Blade due to it acting as a key in some parts of the game. This being said, you can still get the Djinni early.

Second Visit with Sol Blade
The first 3 or 4 rooms are very easy, after that it is quite difficult, although there are quite a few treasures to find. The reason this is complicated is because there is no map whatsoever and Catastrophe is in the no map part of the dungeon.

One method of successfully traversing the dungeon is to use the "left hand rule". Which is a simple way to navigate any labyrinth. Traverse the dungeon by having Matthew's left hand always against a wall, will ensure at very least that you will always arrive back where you started. By using this rule from the second room in the labyrinth, it is possible to navigate the entire dungeon, collect all items, and find the exit (although Retreat Psynergy can be used here) without the use of a map. Equivocally, this works using either the left or right hand side, as long as Matthew never leaves contact with a wall.

At the very end of the dungeon, within the heart of the labyrinth, is an altar with a summon tablet, however, the moment Matthew and his group approach it, the Ancient Devil drops down from above and declares itself the Guardian of Wind. In order to claim the Catastrophe summon, the party must defeat the powerful boss of this secret dungeon.

Collectibles

 * Triton's Ward
 * Mythril Silver
 * Power Bread
 * Psy Crystal
 * Catastrophe Summon Tablet