Retreat

Retreat is a Venus class Utility Psynergy usable in both Golden Sun and The Lost Age that costs 6 Psynergy Points. It is a Psynergy that is inherently known by both Venus Adepts and party leaders within the games, Isaac and Felix, and effectively signifies that they are party leaders. The Retreat Psynergy causes the party to "Return to the dungeon's entrance," and is a very practical spell that can be cast at almost any point in almost any dungeon-style location.

Analysis
While not actually a Psynergy that is mandatory to beat either game, it can be a huge boon to any party wanting to leave a dungeon without having to backtrack through it, one of the best examples being the Tundaria Tower dungeon and another being after Isaac and Garet meet with the Wise One and learn that the Sol Sanctum is about to collapse. It can also be useful during the beginning of a game, if your party of Adepts are injured and you need to return to an inn and want to avoid as many monsters as possible.