Djinn

Djinn are the elemental entities that bolster the Psynergy capabilities of the Adepts. The singular form of Djinn is Djinni. They originated from Mt. Aleph and were spread across Weyard when the mountain erupted.

In Golden Sun and Golden Sun: The Lost Age
There are 72 Djinn and four varieties of Djinn, one variety and 18 Djinn for each of the elements: Venus (Earth), Mars (Fire), Jupiter (Wind), and Mercury (Water). It should be noted that every Djinni's name is a reference to their respective element. Examples include Geode for Venus and Fever for Mars.

While some Djinn are quite easy to obtain and are right out in the open, others hide in the games' overworld. This makes it very difficult for a player that is not assisted by a walkthrough to collect them all. Also, some Djinn must be defeated in battle in order for the player to obtain them while others only need to be interacted with for them to join the party. The Djinn system of gameplay was a highly discussed subject of various reviewers reviewing Golden Sun and The Lost Age.

In Golden Sun: Dark Dawn
In Dark Dawn there are 83 djinn who make an appearance in the game. 72 djinn are usable and collectible throughout the game, and 12 of Isaac's and Garet's djinn appear only in Tanglewood and the Abandoned Mine (one of them becomes a permanent djinn in the party). In total there are 48 new djinn in this game, and 37 djinn don't appear from Golden Sun and The Lost Age at all.

It is unknown if the Warriors of Vale released part of their djinn or if it's canon that they only collected part of the djinn in both games. But one can estimate that at least 120 djinn were released from Mount Aleph instead of 72 which implies that maybe even more djinn were released when Mount Aleph erupted.

States
From a gameplay perspective, Djinn have three different states:

Set
Djinn can be set to any Adept, boosting that Adept's statistics by an amount that varies for each Djinni. All set Djinn increase the Adept's HP by a certain amount as well as that Adept's level in the Djinni's element by one. A character's class, and with it their stats and Psynergy, change depending on how many and what elements of Djinn are set to him or her. When set, a Djinni can be "unleashed" to use their special powers. Although many are attacks (dependent on the Adept's Attack and often containing additional effects), most of these powers are beneficial in other ways, such as healing, bolstering the party's statistics, or one of a variety of effects truly unique to the Djinni (such as Kite and Eddy).

After being unleashed, Djinn are changed into standby mode. Outside of battle, players can change Djinn between set and standby at will. Players can set a standby Djinni during battle as well, although only one Djinni can be set at a time and it will take up that Adept's action for the turn. After spending enough time in recovery, Djinn are automatically set.

Standby
After being unleashed while set, a Djinni enters standby mode. When Djinn are on standby, they can be used to perform Summons, easily the most powerful attacks in the games. In order to perform any given Summon, enough Djinn of the correct element(s) must be on standby. After the Summon is completed, these Djinn are put into recovery. Outside of battle, players can change Djinn between set and standby at will. Players can set a standby Djinni during battle as well, although only one Djinni can be set at a time and it will take up that Adept's action for the turn.

Recovery
After being used for a Summon, Djinn enter recovery mode. While recovering, Djinn cannot be traded between Adepts or changed between set and standby. After spending enough time recovering, Djinn automatically set themselves. During battle, one Djinni for each Adept exits recovery at the end of each turn (not counting the turn they entered recovery). Outside of battle, one Djinni for each Adept sets itself after the party travels a certain distance.

Class Changing and Exclusive Psynergy

 * Main Article: Character Class

Generally, each Golden Sun game can be completely played through with all Djinn Set onto all Adepts of the matching element, so that the Adepts never leave their respective mono-elemental class series such as Squire and Wind Seer. There are several cases in each game, however, where a very temporary switch between Djinn and class series would be necessary so as to have the Growth Psynergy available for on-the-spot use, which is required to make use of plants that would be grown into climbable stalks of ivy. In the first game this is necessary to get several major treasures and Djinn, and in the second game it is even more necessary, for a mandatory dungeon (Magma Rock) cannot be completed without Growth.

Usefulness
It should be noted that some Djinn's unleash effects in battle can be made less useful by other Djinn that do the same thing only better. For example, the Djinni Quartz has a 50% chance to revive an adept to 50% of his/her health, is less useful than the Djinni Dew, which has an 80% chance to revive an adept to 80% of his/her health which is subsequently less useful in TLA by the Djinni Tinder which has a 100% chance to revive a downed adept to 100% of his/her health. It should be noted though, that while some Djinni might become less useful than a new addition, they still retain tactical usefulness by allowing different classes and characters to use abilities not normally given to them. In the above case they allow different classes to access a revive ability without needing to fulfil the requirements to obtain it as a synergy.

Regardless, a Djinni is always offering stat bonuses, class changes and participation in Summons, so all Djinn are necessary to an extent, and one should never be skipped simply because another Djinni exists that does the job a little bit better. This redundancy in Djinn unleashes gives the player more flexibility when setting Djinn on standby before entering a boss battle. In the aforesaid example, Quartz can be safely placed on Standby to ensure a quick summon while leaving a more useful/valuable Djinn such as Sap or Bane set to use their more valuable unleash in the battle.