Alex

A mysterious Mercury Adept, Alex is often thought of as the true villain of Golden Sun, though he really doesn't appear to be a villain. At first, his motives are unknown, but his manipulative nature and apparent lust for power suggests that he has something planned which, in the end, comes to light.

Background
Alex's past is unknown, but it is known that he has a mysterious relationship with Mia, both being responsible for guarding the mighty power of Mercury, and protecting their fellow townspeople of Imil.

In Golden Sun
He later joins the cause of Saturos and Menardi to restore Alchemy to the world, thus betraying Mia and the Mercury clan.