Reveal

Reveal (イマジン, Imagine) is a Jupiter-class Utility Psynergy that allows you to see objects not normally seen to the naked eye. It costs 1 Psynergy Point to cast.

In Golden Sun, Master Hama teaches Ivan the Reveal Psynergy in order for Isaac and the others to survive through the Lamakan Desert by seeking out hidden oases along the way.

In Golden Sun: The Lost Age, Sheba learns the Reveal Psynergy after completing the test at Air's Rock. Maha, from Garoh, was also able to learn Reveal at Air's Rock, but due to his powers stemming from a different source, he was forever trapped in the form of a werewolf.

If you see any objects forming a hexagon of any sort, chances are, there's something in the middle that can only be seen via Reveal. Also, any hidden treasures will be sparkling when examined by Reveal.

Trivia

 * Master Hama's reasoning for directly imparting Reveal onto Ivan is that, while Jupiter Adepts like themselves can gradually learn it over time, the party cannot afford to wait on Ivan to develop it on his own because of the urgent need Isaac's party has for it in their ongoing pursuit of Saturos and his company. However, the lines the English localization of the first game uses to express this are as follows: "Jupiter Adepts can learn Reveal on their own, over time... But that power alone will not help you find Saturos as his company moves on." The odd usage of the phrase "that power alone" to effectively convey "waiting to acquire this power through that method" can potentially be interpreted as Hama spontaneously deciding that Reveal, as a whole, will not be useful for helping Isaac catch up to Saturos.
 * In Dark Dawn, Reveal is effectively replaced by multiple distinct Utility Psynergies: Insight and Search (and Track to a lesser extent), none of which preserve Reveal's ability to show which containers in various towns are holding items that can be added to the player's inventory. Interestingly, only Track is of Jupiter alignment, like Reveal. Insight is aligned with Mercury, and Search is aligned with Venus.