Sith poison was a biological toxin, and a product of Sith alchemy, that when absorbed in sufficient quantity, multiplied the rage felt by a person. In action it was more of a disease, taking up residence in the victim's body and setting off chemical reactions that rapidly diminished the victim's ability to resist the pull of the dark side of the Force. The poison could be fatal unless counteracted by strong Jedi powers, and even then its effects were likely to remain.
Sith poison could either be ingested or administered by medical means, usually via syringe; both of these methods brought a much shorter reaction time upon the victim. It could even be directly applied through the mucus membranes of an already exposed injury.
After being introduced to the body, the poison is absorbed on a molecular level, feeding on the individual's anger and drawing them closer to the dark side. The individual's judgment becomes less rational, and they eventually become so enraged that they begin to lash out involuntarily with the dark side.
Use of Sith poison was extremely rare, therefore being implemented by only the most proficient Sith alchemists. While creating the infusion the alchemist expends much of their own dark side energy; the process is laborious. Once the toxin is finished the alchemist then has a powerful weapon to use against any unsuspecting Jedi.
Krath leader Satal Keto injected Jedi Knight Ulic Qel-Droma with a syringe full of Sith poison shortly before the Great Sith War, when Ulic came to Cinnagar posing as a fallen Jedi. Qel-Droma suffered the full effects of the poison instantly, and involuntarily released the dark side with such force that he destroyed the Krath torture device he was harnessed to. Qel-Droma suffered from outbursts from then on, up until it drove him into murdering his own brother, Cay Qel-Droma. The sudden shock of Cay's death broke the dark side's thrall over Ulic, and of the poison's torment as well.
During the Galactic Civil War, the Dark Jedi Thaum Rystra used Sith sorcery to fix stingers to the lekku of the Twi'lek Desvin Tor'thal, that could fire Sith poison.
Sith poison was first introduced in the Star Wars: Tales of the Jedi - Dark Lords of the Sith story arc, and was one plot device among many used to develop the story of Ulic Qel-Droma's progression down the dark side. It was later elaborated on in the The Dark Side Sourcebook, a supplemental guide for the Star Wars Roleplaying Game.
- "Straight from the Horse's Mouth: A Guide to the Star Wars: Tales of the Jedi Universe, Part 3" — Star Wars Insider 28
- The Dark Side Sourcebook
- The Official Star Wars Fact File133
- Evil Never Dies: The Sith Dynasties on Hyperspace
- Knights of the Old Republic Campaign Guide
- The Complete Star Wars Encyclopedia
- Jedi Academy Training Manual
- Book of Sith: Secrets from the Dark Side