Felix

Felix, an 18-year-old Venus Adept formerly from Vale and the elder brother of Jenna, is the main playable character of Golden Sun: The Lost Age, and for much of both games is made to act as a rival and foil to Isaac.

Background
Felix lived happily with his family and Isaac and Garet in Vale until age 15, when the Mt. Aleph boulder disaster swept him, his parents, and Isaac's father away from Vale, nearly killing all of them. They were rescued by Saturos and Menardi, the ones who caused the disaster by trying to raid Sol Sanctum, and were brought back with them to their home of Prox in the frozen northlands. Felix learns that Prox is in danger of being eradicated by an expanding abyss that exists because of the absence of Alchemy, and that Saturos was tasked to raid Sol Sanctum to acquire the Elemental Stars necessary to initiate the return of Alchemy and therefore save Prox. Thus, to repay Saturos and the other citizens of Prox for saving him and his family, he is trained as a warrior and joins their quest, helping them infiltrate Sol Sanctum a second time three years later.

In Golden Sun
Initially in Golden Sun, Felix fits the role of an anti-hero. From when he first appears in front of Isaac and Garet in Sol Sanctum onward, he demonstrates a noticeably stiff, antagonistic attitude that no doubt developed from years under Saturos' stern tutelage, at one point calling Isaac and Garet "poor fools" for their inability to understand why his and Saturos' party objective is the right one (though he declines to explain it at that point, saying "It's no use talking about it... Just wait and see!").



But for this arrogance Felix has a stronger sense of chivalry which shows when Saturos begins taking previously uninvolved people hostage for the sake of the quest. Felix objects, of course, as his own sister Jenna and the scholar Kraden are taken captive by Saturos, but he is forced to accept these developments. He draws the line, however, when Saturos kidnaps the young Jupiter Adept Sheba, and animosity between Felix and Saturos develops to a strong enough degree that at the aerie of Venus Lighthouse Felix demands to take Sheba back down to ground level for her safety, and is willing to fight Saturos for that purpose. This is right before Isaac's party appears and engages Saturos and Menardi in a climactic duel where the latter two are ultimately slain. When the Lighthouse is activated, the ensuing earthquake causes Sheba to lose her footing and fall off the towering structure, and Felix, having developed enough of a selfless concern for Sheba's well-being previously, dives off the Lighthouse after her, and both appear to be doomed.

In Golden Sun: The Lost Age
Either by luck or by fate, both Felix and Sheba survive their fall and regroup with Jenna and Kraden on the floating island of Idejima. The circumstances of the situation call for him to become the new leader of the effort to restore Alchemy, and so he and his party set off on a world journey of their own to activate the remaining two Lighthouses (the events the player controls in Golden Sun: The Lost Age, during most of which Felix becomes a silent protagonist himself). When he meets Piers and enters Lemuria, Felix learns that the objective to restore Alchemy is more important to the world's life force and welfare than he ever thought possible; he has to activate the remaining lighthouses in order to save not just Prox, but all of Weyard.

When Felix initially encounters Karst and Agatio, Karst declares that she plans to exact deadly revenge upon Isaac for the latter’s slaying of Karst's sister Menardi, and though Felix agrees not to stand in her way when the time comes, the magnitude of what will happen to Isaac becomes enormously apparent to Felix and he develops a serious concern towards who was once a close friend when they were children. This is what drives him to step in and prevent Karst from slaying Isaac at Jupiter Lighthouse and subsequently fight the vengeful Mars Adept in battle. Afterwards, Felix, Isaac, and their respective parties convene in Contigo and Felix finally explains why his objective to restore Alchemy was the correct one, based both on how it will save Prox and free their parents and how it will renew the world's inner life force as it was revealed to him in Lemuria. Isaac, finally aware of the truth, joins Felix's cause, and the two lead their combined party of friends out on the last stages of the journey to break Alchemy's seal.

Felix joins everyone else in their shock and grief when they battle the Wise One's Doom Dragon creation and find that they destroyed their own parents, the ones he had hoped to leave Prox with once the journey was over. However, when he activates the Mars Lighthouse and initiates Alchemy’s return, his parents are revived, obviously placating him and his friends, and The Lost Age ends with him fully reunited with his family and those of everyone else, having finally rediscovered true happiness and friendship.

Unaddressed items
During Isaac's visit to Master Hama, she told him that Felix possessed a fate she would not wish upon any man. Most would speculate that this "fate" would be having to fight his own parents, but others say that it could be something else, since Hama had not told Isaac that he would share the same fate.

There is also the question of why Felix's cape changes from green to blue in The Lost Age, but this tends to not be very relevant.

Fan influence
In fan fiction, Felix has been depicted in romantic scenarios with more people than most Adepts, but most commonly, it is with Sheba in a genre called Lighthouseshipping or in a slash pairing with Piers.