Darth Sion (clone)

This clone of Darth Sion was created by Palpatine in 2 BBY to test Darth Vader's skill. However, when Galen Marek created the Rebel Alliance, Palpatine was forced to turn his attention to other matters. The Sion clone was left sitting for many years.

Creation
In 2 BBY, shortly before Galen Marek's creation of the Rebel Alliance, Emperor Palpatine traveled to the remains of Malachor V and used the Force to rip Darth Sion's molecules from the remains of the planet. Then, he ordered cloners that he had hired privately to use the DNA to create a clone of one of the most powerful Sith Lords of all time.

Neglection
Shortly thereafter, Galen Marek attacked the Death Star, freeing the Rebel leaders but killing himself in the process. This caused Palpatine's attention to turn to senators Bail Organa, Mon Mothma, and Garm Bel Iblis, and he forgot about the clone, which slept undisturbed for many years.

Awakening
In 13 ABY, a Dark Jedi named Desann discovered the clone and awakened it. He told it that it was needed to destroy the Jedi, and the clone went into Desann's service. Shortly after Desann's raid on Yavin IV, in which the Dark Jedi and most of his followers were killed, the clone retreated into hiding on the ancient Sith planet Korriban.

In Service of Darth Krayt
The clone wandered the deserts and tombs of Korriban for over ten years, until finally, a Chagrian with Sith tattoos approached, saying he knew of the clone's power and would like to help him. The clone, sick of roaming the desert, accepted and soon met Darth Krayt. The clone was used by Krayt as an envoy, since the One Sith, as they called themselves, refused to leave Korriban. The clone went on Krayt's errands, killing whoever he was ordered.

More Sith
In 43 ABY, Krayt sent the clone to the planet Kesh, where he met a group of Sith called the Lost Tribe. They said their ship, Omen, had crashed there over 5000 years before. The clone told them of Darth Krayt's One Sith. The Lost Tribe, now stretched across the galaxy, told the clone of Gavar Khai's journeys with Luke Skywalker in an attempt to destroy the Jedi. They said that Khai's daughter had killed High Lord Taalon, and that they would be willing to at least meet Darth Krayt. However, before this meeting could take place, word came that a Sith Lord named Paxis had been killed at the Jedi Temple, and the Lost Tribe launched a full-out war with the Jedi.