The Dragon's Eye is found and made use of in Fuchin Falls Cave in Golden Sun. It is a Quest item which is descibed as "a shining red jewel with flames inside." It is placed into a dragon statue to guide players to the back of the cave, where the Orb of Force is held. Neither the Dragon's Eye nor the Orb of Force is required to beat the game, although players who wish to obtain all the Djinn through a linked game may wish to do so.
Another jewel, using the same sprite as the Dragon's Eye, can be seen in Golden Sun: The Lost Age in the possession of Akafubu. He uses it to move the small statue inside the great Gabomba Statue so that he can receive his special magic. However, the player can not own the Dragon's Eye unless accessed from a debug room.
The Dragon's Eye that can be found in Fuchin Falls Cave does not need to be used to gain the Orb of Force, so theoretically, the player can keep the item in their inventory and transfer it to The Lost Age using the data transfer. However, doing so is inadvisable because the item has no function in The Lost Age but occupies a slot in the inventory that could be used by another item instead, and it cannot be dropped or sold, meaning that if the player chose to transfer it, they would be stuck with it.