Darth Har was a human pirate who worked during th Clone Wars. Following the Wars end Har and his crew continued to work on the Outer Rim until they were intercepted by Imperial fighters. The pirate crew were forced to make a crash landing on Korriban where only a handful of them survived.
Darth Sion and Darth Zealot inspected the crash site, killing all but Har. Sensing the anger and strength Darth Sion took Har as his second apprentice and began to train him as a Sith.