Character class

A Character class is a gameplay-based method many RPGs use to arbitrate the capabilities of playable characters. In Golden Sun and Golden Sun: The Lost Age, character classes serve just this purpose, dictating enhancements to characters' base statistics and what arrangements and elements of Psynergy they may use.

Unlike many RPGs, such as Final Fantasy, characters in Golden Sun games do not specifically select classes to pursue and develop abilities in; Classes are merely "settings" that can be instantly changed anytime based on what their level of skill in a particular element is. This is determined both by their own innate element, as well as how many and what elements of Djinn are Set onto each character.

Classes serve several important roles from a gameplay perspective. Firstly, they add a great deal of diversity to the game, opening up a large number of Psynergy and statistical (and hence strategic) combinations. Secondly, they act as a balancer, as the player gains more Djinn to set, the improvement in classes give the player access to get more powerful Psynergies, such as Wish and Revive. This both serves as an incentive for the player to collect Djinn (and hence complete the associated optional, but more complex, puzzles) and acting to stop the player gaining spells that are too powerful too early on. Because of this, the player's selection of classes can aversely change the outcome of a battle. This is most evident when the Monster Skill Djinn Storm is used on the player. The removal of all Djinn cripples an otherwise strong party by reverting the Adepts to their default classes, which serves to make the battle much more challenging. By extension, this is also a feature that balances the powerful summon sequences, as putting a Djinni on Standyby stops it from influencing an Adept's class, hence weakening the party, which in turns creates a tactical dilemma that forces the player to think more carefully about their actions.

"Trees"
There are four "trees" of classes: Mono-Element, Duel-Element, Tri-Element and Item Dependent (The Lost Age only).

Mono-Element
The Mono-Element classes (also called the "Default" classes) involve having only one element of Djinn to a particular Adept and that element is the element the Adept is aligned with (Water for Mia and Piers, Fire for Garet and Jenna, etc.) and all through the progression of the class, only one type of Element is needed. The classes stem from the base class of the character (EG: Felix and Isaac being Squires follow the Squire class tree.)

Pros of the Mono-Element Classes

 * Simple, straight-forward and easy. Sticking to the Mono-Element classes will get the job done without much fanfare.
 * Using Djinn and summons in battle do not carry the potential of crippling an Adept with an undesired, and perhaps dangerous, class switch.

Cons of the Mono-Element Classes

 * Each one has one or two painful shortcomings, such as terrible stats in one area, (for example, the Guard class series has the worst agility of all the classes, and the second worst PP stat (this is only compounded with expensive Psyenergies like Volcano and Liquifier), while the Water Seer class series has lackluster agility and a bad offensive Psyenergy lineup).
 * Each class has only a single element worth of Psyenergy, which can prove annoying when facing enemies who have a high resistance to that particular element.
 * A few quick Djinn trades into the Duel-Element classes can quickly patch up these shortcomings.
 * Small array of Psyenergy at your disposal.

Duel-Element
The Duel-Element classes require having a majority of Djinn from another element, and several Djinn of the Adept's own element for the higher levels.

Pros of the Duel-Element Classes

 * Fairly easy and straightforward, though not as much as the Mono-Element classes.
 * Quite often they will patch up the shortcomings of the Mono-Elements with an improvement to the Mono-Element's strengths with very little sacrificed (IE: Mia to a Hermit).
 * Adepts have two elements of psyenergy in their arsenals, allowing them more flexibility against monsters with a high resistance to one element.

Cons of the Duel-Element Classes

 * Some care must be taken when using Djinn and summons so as to not accidentally shift the Adept into an entirely different class tree.
 * Some care must be taken when selecting duel-elemental classes that you don't exasperate an already painful shortcoming (Isaac, Felix and Garet to a Brute)
 * A look at the Tri-Element classes might be more than enough to skip this tree altogether.

Tri-Element
The Tri-Element classes require two different types of Djinn attached to the Adept.

Pros of the Tri-Element Classes

 * Statistically, the Tri-Element classes are the best, and any shortcomings they might have can easily be compensated for by their other stats (such as the Ninja class series's sub-par defense being compensated for with the highest Agility and second highest attack).
 * Three elements worth of psyenergy in the Adept's arsenal allows for great flexibility against monsters.
 * Tri-Element class possess some hard hitting Psyenergies and quite often have a PP pool to run with it (such as Quick Strike in the Samurai class series, and the Thunderclap Psynergy series in the Ninja class series).

Cons of the Tri-Element Classes

 * The Tri-Element classes are tactically challenging and great care must be taken when using Djinn in battle to avoid an unwanted class change.
 * Djinn Storm might be more of a death sentence then it already is, especially if your handling the fight with limited summons, as on their own, the Tri-Elemental classes pack a hard punch.

Item-Dependent
The item dependent classes require the item that grants the class to be equipped (Trainer's Whip for Tamer class series, Mysterious Card for Pierrot class series and Tomegathericon for Dark Mage class series) and 1, 2, or 3 (for the 2nd, 3rd and 4th levels) Djinn of each Element that is NOT the Adept's base element.

Pros of the Item-Dependent Classes

 * Possess psyenergy from each element allowing unparalleled flexibility.
 * Possess psyenergies that are unique to each class.
 * Statistically sound, strengths make up for weaknesses (the Tamer's dismal PP pool is offset by its incredible attack, and the fact that most of its Psyenergies draw on the attack stat when calculating damage).
 * Even with all Djinn on standby or recovering, the Adept maintains the first tier of the class (EG: Isaac, equipped with the Mysterious Card, would revert to a Pierrot and not a Squire when all of his Djinn are on standby or recovering).
 * When unleashing Djinn, it's fairly easy to maintain the class of the Adept in question.

Cons of the Item-Dependent Classes

 * Only one of each may be present at any time.
 * Requires three elements worth of Djinn.

Which to choose?
Which classes and combos you use is entirely up to the player in question. Experiment and see what you like and don't like.