Crystalis

Crystalis, originally released in Japan as God Slayer: Haruka Tenkuu no Sonata (ゴッド・スレイヤー はるか天空のソナタ), is a 1990 action-adventure RPG produced by SNK for the Nintendo Entertainment System.

Though Crystalis never became a runaway hit, it is now considered a cult classic. The game's initial success prompted a release for the Game Boy Color by Nintendo Software Technology in 2000, which is generally considered more of a remake than a simple port. Many changes were made to the story, music, and other aspects of the game, upsetting fans of the original.

Plot summary
Crystalis takes place in a post-apocalyptic world, one hundred years after a global thermonuclear war has reverted civilization to a primitive, medieval existence populated with fierce mutated creatures. Science and advanced technology have been abandoned though the old ways of magic have survived. The survivors of the terrible destruction built a floating "Tower" to prevent any future cataclysms, as its occupants would have the power to govern the world due to the Tower's weapons systems. A man known as Emperor Draygon, however, has revived the forbidden ways of science and combined them with magic. With these skills, he controls the world's last remaining military power and seeks to conquer what's left of the planet by attempting to enter the Tower.

The protagonist is a young man who has been cryogenically frozen since the time of the devastating war one hundred years earlier. He awakens in the future with no memory and, guided by four wise sages, gradually learns that the world is sinking into turmoil once again, due to the Draygonia Empire's destructive influence. Entrusted with the Sword of Wind, he seeks to aid Mesia, another survivor from his time, and to combine the four elemental Swords of Wind, Fire, Water, and Thunder into the legendary sword, Crystalis. Together, they must defeat Draygon before he uses the Tower to achieve his evil ambitions.