Legacy of the Darksaber

In the days of the Old Republic, the Darksaber was kept at the Jedi Temple after the passing of its creator, Tarre Vizsla, the first Mandalorian ever inducted into the Jedi Order. However, it was taken by Mandalorians of House Vizsla, who raided the Jedi Temple during the Old Republic's fall. Descendants of House Vizsla used it to kill many Jedi and rule all of Mandalore for many years.

Taken from Star Wars Rebels 3.15: Trials of the Darksaber