Siss

Siss was a clone of Zam Wessell. He was part of a massive "Counter-Clone Army" developed by the Separatists, but the force was wiped out. During the cloning process, a malfunction happened. The X Chromosome of the clone failed and they had to replace it with a Y Chromosome. This resulted in a male clone. Renamed "Siss" by his cloners, he eventually became Darth Siss. He tried to recreate the CIS but was killed on Sarapin.

History
After birth, Siss was ultimately disgusted by his fellow clones for being a male. In addition, his genetic code was damaged further so he could no longer shapeshift. Even the cloners that made him found him useless, but he made up for being a "freak" by being the finest clone soldier in the Counter-Clone Army. After seeing he was different, Count Dooku took him under his wing and began to train him as a secret Dark Acolyte. The training did not last long, however, as Dooku was killed by Anakin Skywalker aboard the Invisible Hand. Siss fled after learning of this and possibly escaped death, as his entire clone force was destroyed in the Battle of Saleucami. He was not seen for years.

Life After the Galactic Civil War
In 11 ABY, Siss appeared and shyly joined Luke Skywalker's Jedi Academy. He made virtually no friends, but he did get along with Desann. He was devastated when his former friend became a Dark Jedi and assisted the others in the protection of the Praxeum against Desann's Reborns and Shadowtroopers. After that, he became the padawan of Master Plo Koon, a Jedi who survived Order 66. Koon, however, did not pay a lot of attention to his padawan, who began to research the Dark Side once more. Slowly, he became corrupt and fled to Krant.

CIS: Recreation
Siss realized that being a Jedi would bring him nowhere. Therefore, he found a broken down B3 Super Battle Droid in the remains of a moon of Naboo, the former residence of the late Chadias Markith. Using the mechanics of the droid, he built a massive army and rebuilt Sev'Rance Tann's Droid Foundry on Krant, using it as a base. The New Republic and several Jedi, including Leia Organa Solo, Luke Skywalker, and Plo Koon, assaulted the base and destroyed a lot of the droids, although most of them escaped with Siss. Siss then declared himself Darth Siss and briefly went to Ilum to build a lightsaber. He then went to Sarapin, using the ruined CIS base on Mt. Corvast to create a new army. He was also contacted by General Holocaust, a former clone who wished to destroy the Republic. The two joined forces and prepared for an attack. Finally, it came. Holocaust led the army into combat, while Siss himself cut down the Jedi. After a long lightsaber duel, he killed Plo Koon and almost killed Skywalker. He was caught off guard when Republic soldiers, wearing lava-proof armor, emerged from the lava rivers and attacked his base in a flanking maneuver. Luke used this distraction to cut Darth Siss down. The base was destroyed shortly thereafter.