The Code of the Sith, known as Qotsisajak in Sith, was the mantra that reinforced the core beliefs of the Sith Order. It was considered the dark side counterpart to the Jedi Code, and was first authored on the planet Ziost in 6900 BBY by the Jedi heretic Sorzus Syn. The code remained remarkably unchanged through the millennia, as the Sith Lord Darth Bane still taught the words of Sorzus Syn when he began rebuilding the Sith Order around 1000 BBY, after the Seventh Battle of Ruusan.

According to the Human Qordis, founder and master of the Sith Academy on Korriban, the Code of the Sith served as the backbone of the Order since Jedi Exiles enslaved the red-skinned Sith Purebloods from the Horuset system. Indeed, the first recorded appearance of the Code dates back to the personal journal of Sorzus Syn, one of the fallen Jedi who set foot on Korriban in the year 6900 BBY.

Syn had been impressed by the lifestyle of the Sith Purebloods, who would take all what they needed, kill the rest, and use everything to its fullest. Inspired by their example of brutal impulsiveness, Syn decided to write a pendant to the Jedi Code, a new mantra that was based on passion and the channeling of rage through anger. In her journal, Sorzus Syn stated that the Jedi beliefs only encouraged acceptance of one’s limitations and passivity. The Sith Code was created on the planet Ziost so as to point to the «failings» of the Jedi Code, and it was meant to become a unifying mantra for the followers of the newly created Sith Empire.

By 990 BBY, the Jedi Order knew of the Sith Code. In The Jedi Path: A Manual for Students of the Force, the Human Chief Librarian Restelly Quist wrote a chapter on Sith history, including a brief commentary on the Code of the Sith. According to Master Quist, the tenets of the Sith were self-centered and focused on individual needs and desires, while the Jedi defended the idea of achieving greatness through self-humbling.