Once a heroic Jedi Knight, Darth Vader was seduced by the dark side of the Force, became a Sith Lord, and led the Empire's eradication of the Jedi Order. He remained in service of the Emperor -- the evil Darth Sidious -- for decades, enforcing his Master's will and seeking to crush the fledgling Rebel Alliance.

Was Vader a Sith master?

Though Darth Vader never attained the rank of Sith Master, he secretly instructed his own Sith apprentice in a plot to overthrow the Emperor. ... the grandson of Darth Vader, Caedus anointed the Jedi Tahiri Veila as his apprentice, and thus continued the Rule of Two until his own death in 41 ABY.

Why is Darth Vader a Sith Lord?

The Galactic Empire was ruled by the Sith Lords Darth Sidious and Darth Vader. Not too long after Tyranus was sacrificed and betrayed by Sidious, Anakin Skywalker was turned to the dark side and became the Sith Lord Darth Vader, while Sidious ruled the galaxy as Emperor.