Sith’ari was a title that, in the ancient Sith, meant «Lord» or «Overlord,» first claimed by King Adas. After Adas’s death, the term became the subject of a legend prophesying the coming of a being that would lead and destroy the Sith, but in doing so would make the Sith more powerful than ever before. In this context, the term came to mean «perfect being» or «god.»The prophecy, which was in many ways similar to the Jedi prophecy of the Chosen One, retained its significance for the Dark Lords up until the time of the Order of the Sith.

Sometime during the early history of the First Sith Empire, the coming of the Sith’ari was foretold. Inspired by the legend of Adas, the Sith’ari, referred to sometimes as «the prophesied one,» was to be a perfect being, free of all restrictions—the ultimate Sith. The Sith’ari would rise to power to lead the Sith and, according to the legend, destroy them—yet, through their destruction, make them stronger than ever.

Some of the students at the academy on Korriban thought Sirak was the Sith’ari. However, Sirak was killed by his nemesis, Bane. Darth Bane, eventually becoming a Dark Lord of the Sith, finally fulfilled the prophecy in many ways, first by providing Skere Kaan with the thought bomb, which caused the annihilation of the Brotherhood of Darkness, and then by instating the Rule of Two, leading to a powerful line of Sith by reducing their numbers to only two at a time. This allowed the dark side to distill in two vessels only; whereas Bane believed that its power in the past had been spread far too thin among the vast numbers of Sith ‘lords’. This concentration of strength also made it easier to hide the Sith until they built up enough power to destroy the Jedi, and thereby open the way for the Sith to rule the galaxy.

Although Darth Plagueis, due to being a creature of logic and not superstition, never believed in the Sith’ari prophecy, or any prophecy since he considered prophecies «wishful thinking», he nonetheless saw no reason to not claim the title figuring that it ultimately fit him.

Almost a century later, Darth Sidious proclaimed himself to be the perfect being of ancient Sith prophecy while killing his master, Darth Plagueis, in his sleep.