Devil swords

This world is all about swords and swordsmanship. Skilled warriors are looking for famous "devil swords", as they can grant extraordinary abilities, unlock new stages of powers and do much more. They say that even average swordsman with such sword can easily beat majority of warriors from entire world. You got lucky and finally found yours in a dungeon. What kind of powers will it grant you? Can you master it, unlock new stages and become the best swordsman in the world?