Red Key

In Golden Sun, the Red Key (あかいかぎ Red Key) is found on the third level of Crossbone Isle. It is used to open a red door that keeps players from moving on to the next level.

In Golden Sun: The Lost Age, the Red Key is an item found in the Jupiter Lighthouse. It grants access to one of the two "towers" where the player must activate a statue figuring a bowman in order to open the top of the lighthouse. The Red Key found at Crossbone Isle in the first game can also be transferred to the second game by using data transfer. However, its description will tell you that it's a key to a door in Jupiter Lighthouse, not Crossbone Isle.