Crystalis

Crystalis is an Action/RPG video game produced by SNK in 1990 for the Nintendo Entertainment System. It was released for the Game Boy Color in June, 2000, with a different storyline, new music, and some other minor modifications.

In Japan, Crystalis was called God Slayer: Haruka Tenkou no Sonata (God Slayer: Sonata of the Far-Away Sky).

On the NES, Crystalis utilized the MMC3, a standard Memory Controller that allowed access to >64kb ROM.

The story is as follows: On October 1st, 1997, a war breaks out across the world. During the fighting, the Earth's axis shifts, and mutant creatures begin to appear. The survivors realized that the war caused the shift, and vowed never to cause war on such a scale again. They erected a monument in the sky to "oppress evil forever".

Over the course of 100 years, the mutant creatures began to take large portions of the world. The survivors, meanwhile, have fallen back to more primitive times. Small villages dot the landscape, hidden away in valleys and mountain passes that are still safe from invasion by creatures. Magic, meanwhile, has crept back into the world, and magical swords and other trinkets exist. Medicine has faded to herbalism, and religion has reverted to superstition and animatism

In these small villages, rumors of The Tower, which was meant to oppress evil, grew sinister. Rumors appeared, suggesting that the Tower would destroy humanity if evil returned to their lands.

Only one hope remains, the Crystalis, a powerful sword that can only be formed from four Elemental Swords.