Alex

Alex is a Mercury Adept from Imil who is among the last of the Mercury Clan. He is widely interpreted by fans as the main villain of the Golden Sun series. An intriguing blend of bishōnen characteristics and Machiavellian motives, Alex's character is not outright evil, merely manipulative (he outright boasts his ability to discard people who are no longer "of use" to him late in the story).

Background
Alex once lived in Imil as Mia's apprentice, and both held the responsibility to act as healers and protectors of the populace. (It is suggested in the Japanese version of Golden Sun that he was the apprentice to Mia's father.) It is unclear what drove him to a strong desire for power and self-gain, but it is known that he encountered Saturos sometime after the incident at Vale and enlisted himself into his band of warriors that would aim to restore Alchemy to the world, at which point he clearly had his master plan already hatched: he would dupe Saturos and attempt to steal Alchemy-based power for himself at the location where Alchemy's return would be initiated, the peak of Mt. Aleph. Thus does he abandon the life of a healer and betray Mia when he departs with Saturos.

In Golden Sun
Initially, all goes well as Alex helps Saturos, Menardi, and Felix raid Sol Sanctum and activate the Mercury and Venus Lighthouses, with Isaac's party in hot pursuit to halt their objective. At the aerie of Mercury Lighthouse, Alex encounters Mia for the first time since he left. He seems only minimally disappointed when Mia expresses her contempt for Alex's betrayal and apparent madness in assisting Saturos, and as he leaves with Saturos he leaves behind the message "Ah, well... I can't stay the same Alex you knew forever..." When the Venus Lighthouse is lit, however, Saturos and Menardi are slain by Isaac's party, and Felix takes on the new role as leader of the rest of the effort to break Alchemy's seal. Alex decides to abandon Felix at this point and set out on his own, deciding to become a neutral party.

In Golden Sun: The Lost Age
Alex's self-prescribed stance as a neutral party who will assist those who aim to break the seal of Alchemy becomes apparent when he encounters Karst and Agatio and sees their vengeance against Isaac for the death of Saturos and Menardi. He leads the Mars Adepts to Felix in the seaside town of Champa, where Karst's threats to Felix convince the latter to hurry up in his objective to light the remaining Lighthouses, which of course is what Alex would appreciate himself. Later at the Jupiter Lighthouse, when Karst and Agatio carry out their revenge upon Isaac, Alex notices that Felix certainly would rather save Isaac before lighting Jupiter, and that is why Alex appears before Felix and restores his health before letting him confront Alex's supposed companion Karst. In helping Felix, Alex indirectly causes Jupiter's activation sooner. When Karst takes the Mars Star and engages Felix in battle, Alex stops one side from slaying the other because, now that Karst and Agatio are the ones with the Mars Star, it is up to them to activate the final Lighthouse.

After a complex series of dramatic events and revelations among everyone else at the Mars Lighthouse, all four Elemental Lighthouses are now activated, and the process that returns Alchemy to Weyard begins in earnest. Alex scrambles to the top of Mt. Aleph and stands in the center of the forming Golden Sun's stream of energy into Mt. Aleph, gaining bolstered Psynergy power and near-limitless life. At this point, ecstatic with his success, he throws mercy to the wind and attempts to summon a storm to attack Vale below as a test of his newfound power. To his great irritation, he fails to conjure so much as a cloud, and the Wise One appears before him, stating that a side-effect the Wise One took long ago has caused Alex to gain most of the power of the Golden Sun, but leaving a small portion of the power of the Mars Star to the care of Isaac, in turn denying Alex full mastery of Alchemy's powers. Enraged by the Wise One's deceitful ploy, Alex attempts to attack him with the Psynergy he has, but the Wise One renders Alex's body immobile. Then the mountain and the landscape surrounding it begin to mutate and collapse due to Alchemy's newly released influence, and Alex seems to disappear into oblivion.

Fan influence
Alex is a versatile character for fan fiction authors to depict. While many stories have him acting in an outright villainous manner, others depict him in more troubled personal states. Alex is also depicted with a gentler side from time to time, mostly in stories taking place before the original Golden Sun; this is illustrated by the fact he has his own list of Shippings.