Spice

"Spice, in any of its dozens of varieties, was the plague on the galaxy; a horribly addicting drug that its victims would lie, steal, assault, and murder for."

- Reflections of Eli Vanto

Spice was the name for a type of illicit substance or substances in demand throughout the galaxy. Spice was mined at the spice mines of Kessel, where Wookiee slaves were worked to death turning medicinal spice mineral into a dangerous drug. Spice mines could be found in several other planetary systems throughout the galaxy, including those of Ryloth and Naboo. One variation of the narcotic was known as ryll, was mined on the planet Ryloth and had both scientific and recreational applications. Sansanna spice was a type of spice that could be found throughout the galaxy.

History
The Pyke Syndicate used raw spice to create a powerful drug and Supreme Chancellor Finis Valorum sent Jedi Master Sifo-Dyas to investigate.

An assassination attempt against Senator Padmé Amidala was initially suspected to be the work of disgruntled spice miners on the moons of Naboo, though it later transpired that the assassin was in fact hired by Count Dooku, the leader of the Separatists.

When the Ohnaka Gang captured Count Dooku, they demanded a million credits in spice delivered in an unarmed diplomatic ship in exchange for handing him over to the Jedi. After Obi-Wan Kenobi and Anakin Skywalker were captured during a meeting to verify that the pirates did indeed have Dooku, the Gungan Jar Jar Binks and Senator Kharrus were sent with the demanded spice, though it was rendered irrelevant, as Dooku had already escaped by the time they arrived with it.

Imperial Moff Delian Mors was a known user of spice, and Colonel Belkor Dray noted that she could operate well despite its effects.

Ensign Baz was a known spice user and because of this was relieved from duty on the Carrion Spike by Moff Tarkin during a voyage to Coruscant shortly after an attack on Sentinel Base.

Imperial Moff Ghadi used a variant of spice known as polstine spice to blackmail Arihnda Pryce, then an aide to Lothal Senator Domus Renking. He described the spice as "highly prized, highly expensive, and highly illegal", and evidently even a light dusting on one's clothes was enough to guarantee a life sentence in prison.

A pre-spice variant called scarn was the subject of a land dispute between the native Cyphari of the Afe Clan led by Chief Joko and the human colonists led by Mayor Pord Benchel. The land dispute was engineered by human colonists Clay Tanoo, Lenora Scath, Brigte Polcery, and mercenary Nightswan as a means to gain access to the large scarn vein under the Afe Clan land. The conspiracy was quickly unraveled by Commander Thrawn and ensign Eli Vanto, who brought a swift end to the land dispute by scorching and destroying the scarn vein with the help of TIE fighter pilot lieutenant Gimm and Lieutenant Commander Osgoode.

When Imperial forces boarded the Tantive IV, C-3PO was worried that he and R2-D2 would be sent to the spice mines of Kessel.

Behind the scenes
It has been inferred that Frank Herbert's seminal book, Dune (1965), influenced Star Wars heavily. Spice plays a central role in the Dune universe.

Spice was first mentioned at the beginning of the original Star Wars with C-3PO's worry to R2-D2 that "We'll be sent to the Spice Mines of Kessel, smashed into who-knows-what!" Spice was also briefly mentioned in Attack of the Clones of the prequel trilogy and a payment of spice was an important plot element in two installments of Star Wars: The Clone Wars. In canon, the details of what, exactly, spice was were kept quite vague until "The Lost One" in Star Wars: The Clone Wars, which clearly identified it as being used to make a dangerous drug, corroborated by reference material for Star Wars Rebels clearly establishes it as a dangerous drug. Numerous stories from the Expanded Universe, later re-branded as Star Wars Legends gave details on the spice trade, describing it as consisting a number of different types of mind-altering drugs, such as ryll and glitterstim.