Belia Darzu

Belia Darzu was a female Shi'ido changeling and Dark Lady of the Sith who reigned from 1,250 to 1,230 BBY, in a period of the New Sith Wars known as the Sictis Wars. She crafted a suit of heavy battle armor that was imbued with dark side powers, which granted her invisibility and boosted her physical strength. The armor was reportedly worth 37,000 credits.

Belia Darzu also used nanogene technology to create an army of Technobeasts which she controlled with mechu-deru, an ancient form of Sith Alchemy that infuse mechanical objects with dark side energy. This power was believed to have been lost by the era of the New Jedi Order, but Roganda Ismaren discovered several ancient scrolls which documented its usage.

Darzu was killed on Tython when she was poisoned by the Mecrosa Order at the behest of her fellow Sith Lords.

Behind the scenes

 * Like many other Sith Lords, even those who did not go by Darth, Darzu's name is based on something else: the demon Belial.
 * According to Abel G. Peña, "In the Dark Side Sourcebook, there is an illustration of a woman in, I believe, the Dark Side Marauder section. This same woman appears in the changeling section of the Ultimate Alien Anthology. I give you Belia Darzu." 
 * In Star Wars Miniatures Belia is named Dark Side Enforcer (9/60 CotF).