Sabbathius Osbourne

Sabbath Osbourne was a Dark Lord of the Sith several years after the death of Emperor Palpatine. It is likely that Osbourne was one of Palpatine's Dark Side Adepts, and was trained by the Emperor himself. It's also likely he received further training by Wyth Skellheim, an earlier Dark Lord.

It is unknown if Osbourne ever took an apprentice, though it is likely he had a hand in the training of Bacharan Valak, the future Emperor.

In 6 ABY, Dark Lord Osbourne, along with Grand Moff Caldny, leader of the Interim Ruling Council, and Admiral Russel Canis, initiated the Battle of Etti IV where he succeeded in kidnapping New Republic hero Han Solo. From there, Osbourne was hunted by the Jedi to Palanhi, where he fought against Luke Skywalker, Leia Organa Solo and other Jedi. Osbourne escaped from the Duel on Palanhi with Solo, though Solo would later be rescued.

By the time of Valak's rise to power in the remnants of the Empire, Osbourne had disappeared - likely slain by Valak himself.