Marth is driven from his homeland in his youth by the forces of the Dolhr Empire, led by the Shadow Dragon Medeus. He flees to a remote island, with a handful of allies in tow, and remains hidden there until the time comes to rally his allies and mount a resistance.
His liberation forces push all the way to the empire's doorstep, and with the aid of Falchion, a legendary sword passed down through the royal family, Marth seals Medeus away.
The Shadow Dragon is later revived by the Dark Pontifex Gharnef, but Marth defeats him again and finally ushers in an age of peace for all Archanea.
From that day on, the people extol him as their "star and savior."