Super Saiyan Original Art

The ability to become a Super Saiyan was once considered to be nothing but a legend, as it had not been performed for over one thousand years. Vegeta stated that a Super Saiyan has achieved a level of power so overwhelming that it could only be maintained in a transformed state. Despite only being told through legend, Frieza, who had Saiyans in his army, became paranoid over the possibility of truth behind the legend due to the constantly growing power of the Saiyan race. After receiving informal permission from the God of Destruction Beerus, Frieza finally decided to annihilate the Saiyan race by destroying Planet Vegeta, thus apparently sparking the end of the Super Saiyan legend. However, twenty-five years later, the Super Saiyan legend was proven true when Goku accomplished the feat during his titanic battle with Frieza. via DBWiki