A chest (also Treasure chest) is a common containment unit used throughout the Golden Sun series. It is a significant gameplay element and is encountered often through the player's journey. Each chest always contains an item that can be used by your party; sometimes a rare consumable item such as a cookie, but most notably artifacts, weapons and armor that are much more powerful and unique than common stock. Opening every chest you can reach is generally a mantra one typically follows when playing the games, because some chests contain items that are required to make progress.
The treasure chest has long been a staple element in "traditional" fantasy-themed Role Playing Games, and Golden Sun games are no different in that respect. Golden Sun has a slight twist with chests, however: in each game, a select number of chests are actually not treasure chests at all, but unique boss-like enemies called Mimics that the player must battle before getting its item. There are 8 in Golden Sun, and 9 in The Lost Age. They can be distinguished from regular chests only by the fact that they are more easily reachable than most chests. Therefore, it is wise to save the game before interacting with a suspected chest if the party is exhausted.