How do you translate the phrase Darkness Blade to Japanese and how do you pronounce it?

Literally translated, light blade would be 'hikari no katana,' written:　光の刀 I would suggest that instead of "dark blade," you go with "shadow blade/blade of shadows," as not only does it sound better than the literal translation of "dark blade," but also stands better as an opposite to a "blade of light." That would be 'kage no katana,' written: 影の刀