In the first game of the Golden Sun series, Felix is a member of the group opposed by the main character. Whereas Isaac believes that unleashing the power of Alchemy will spell the end of the world, Felix believes that is the only way it can be saved. Though the first game's objective is to thwart Felix's party, in Golden Sun: The Lost Age the perspective changes to Felix and the player advances his quest to awaken Alchemy.
He hails from the same hometown as Isaac, Vale, where he lived with his two parents and sister Jenna. Three years before the adventure begins, a fierce storm ravaged the village and Felix was swept downstream. He ended up being rescued by Saturos and Menardi, whose quest he subsequently became involved in. Like most residents of Vale, he is an Venus Adept.
A man of few words, especially in The Lost Age when he becomes a silent protagonist (concurrently, the formally silent Isaac gains the ability to speak when he's no longer the main character). Though he has a cold demeanor, he's fiercely protective of his friends, especially Sheba, who he would jump off a tower for. And kinda did. He will do whatever it takes to do what is right, and cares little if he winds up looking like the bad guy for it.
Felix was raised in Vale with his sister Jenna, both of whom were friends with Isaac and Garet. During the prologue of Golden Sun, he was caught in the raging river. His parents, as well as Isaac's father, attempted to rescue him, but their efforts were for naught when a gigantic boulder from Mt. Aleph broke through the town's barrier. Felix was swept away, and presumed dead.
In reality he was rescued by Saturos and Menardi, a couple of elite Mars Adepts on an important mission to light the four Elemental Lighthouses and restore the power of Alchemy to the world. Felix is recruited on their quest, and three years later they return to Vale to steal the sacred Elemental Stars - vital artifacts for their mission - from the nearby Sol Sanctum. They're met with Isaac and co. who don't intend to let them do that, to which Saturos and Menardi respond by making hostages of Jenna and local scholar Kraden. Things get out of hand, Sol Sanctum collapses, and Felix's party of villains and hostages escape and begin their task of lighting the Lighthouses, pursued ever closely by Isaac and his growing band.
With the aid of the Mercury Adept Alex, they gain entry to the Mercury Lighthouse and activate it with little trouble. Lighthouses can only be opened by Adepts with the respective elemental alignment. Their group has all bases covered except for Jupiter, so intrepid leaders Saturos and Menardi do the only natural thing and kidnap a Jupiter Adept. Felix, though still determined to see the mission through for the good of the world, is beginning to get a little tired of the rampant kidnapping and general villainy. That, combined with the fact that he comes to have a liking for Sheba, leads Felix to disobey orders in the Venus Lighthouse, not wanting to leave her alone with Saturos. He insists that she be taken to safety for now. Not ones to tolerate disobedience, the two Mars Adepts decide that Felix is of no further use for them. Before they can dispense punishment, Isaac's party arrives on the scene to save the day. They manage to defeat Saturos and Menardi, and Felix thanks them by saying he's going to continue lighting the rest of the Lighthouses anyway. As a result of beacon being lit, the earth quakes violently, and Venus Lighthouse begins to fall apart. Sheba is knocked off the tower, and the ever-heroic Felix leaps off after her. Isaac and friends are left dumbfounded.
Defying more than a few odds, the two survive the fall. After meeting back up with Jenna and Kraden, the adventure continues. As hijinks ensue, Felix struggles with whether undoing the seal on Alchemy is truly the right thing to do. With the help of Piers, research is done on the matter. Discovering evidence that the world is indeed slowly withering away without the power of Alchemy to support it, they become more resolved than ever to see their mission through. At the Jupiter Lighthouse they finally encounter Isaac's group and have some words. They settle their dispute, Isaac is convinced that activating the Lighthouses might be the best option after all, and both groups join forces.
Felix leads everyone to the Mars Lighthouse, and they successfully break the seal and reawaken Alchemy to the world.
Felix makes no appearance in Golden Sun: Dark Dawn, though the dramatic effects of his controversial efforts to unseal Alchemy are seen throughout the world. Matthew, the game's protagonist, is his nephew.