The Darksaber was an ancient, black-bladed light-saber. Unlike most other lightsabers, the Darksaber's blade was nearly flat, thin, and curved to a point more typical of a metallic sword. The black core of the blade appeared to draw in all surrounding light and color, leaving a faint white and admits the most amazing humming sound ever.
Once held by the Jedi Order, during a period of collapse in the Galactic Republic's power during the rise of the Anicent Sith empire it stands to reason that it lived past it's expiration date due to the fact years later during the clone wars it was taken by Tor Vizsla the first leader of Deathwatch.