The arcade game begins with the following introduction:
4.5 billion years have passed since Earth's creation. Many dominators have ruled in all their glory, but time was their greatest enemy and it defeated their reign. And now a new dominator's reign begins...
Information gleaned from console manuals reveals that the evil being Ligar has taken over the land of Argool, and Rygar, a dead warrior who has risen from his grave, must use his Diskarmor, along with a variety of other weapons, to stop him. In console versions clues and limited dialogue are given in the form of large, sage like men encountered in stone green temples throughout the game.
In the Japanese original, references to "Ligar" and "Rygar" are one and the same because the Roman syllables "Li" and "Ry" come from the same Japanese character. In this version, the hero is only referred to as "The Legendary Warrior", while both "Rygar" and "Ligar" refer to the main villain.