...what would it entail?
I have a few ideas kicking around in my head. The game would take place 1000 years before Phantasy Star. One of the main player characters would be Tarzimal, Lutz's mentor/instructor from Phantasy Star. Among other things, he taught Lutz the secret of being suspended in cryogenic sleep for a millennium. Dark Force would obviously be the main antagonist. I am thinking that two (seemingly somewhat minor) aspects of Phantasy Star would play a large role: the Forgotten Tower containing the Laconian Sword, and Damor the Soothsayer. Damor would be DF's understanding and the penultimate boss of the game. Like Lassic in PS1, Damor had the power to destroy everyone in one hit, with only the crystal being able to prevent this. Damor isn't defeated; he is simply neutralized. Damor is immortal, having been given this power by the Darkness. Damor ends up having amnesia, and he is trapped atop Baya Malay with the very crystal that prevented the heroes from dying. In addition to the crystal, a sword made from Laconia, a very rare and seemingly mystical metal found deep underground in Dezoris, was the only thing able to pierce Damor's defenses. After beating and neutralizing Damor and defeating Dark Force, the sword was left in a tower on a small island deep in the ocean, and a dragon is left guarding it. The protagonists were terrified of its power, and thinking that Algo was free of Dark Force's terror, they left it in a place that they thought no one could find it.
Any other ideas?