Daishii Kann, also known as Darth Sidious, was a Force-sensitive Tenshi male who served as the last Supreme Chancellor of the Galactic Republic and the first Emperor of the Galactic Empire. A Dark Lord of the Sith in the Order of the Sith Lords, recorded by history as the most powerful who had ever lived, his entire life was the culmination of a thousand-year plan to overthrow the Republic and the Jedi Order from within.  

Born in 95 BBY on the planet Naboo to the aristocratic House Kann, Kann discovered the Sith at a young age as a collector of dark side artifacts. In 78 BBY, he met Meki Ura, a Makai businessman who was in reality the Sith Lord Darth Plagueis. Under Plagueis's manipulation, Daishii killed his father and pledged himself to his new Master's dark side teachings as Darth Sidious. Kann lived a double life for many years, serving an untarnished career as Naboo's ambassador in the Galactic Senate, and later the Jedi Order as both a Jedi Master and member of the Jedi High Council, while learning from his master and training a young Dathomirian as the Sith assassin Darth Maul. Plagueis and Sidious, both exceptionally skilled and powerful in the Force, were able to conceal their identities from the Jedi for decades. As Plagueis privately searched for the key to eternal life, Sidious manipulated galactic politics, culminating in the blockade of Naboo by the Trade Federation. In the wake of the political crisis, the Galactic Senate voted to elect him as Supreme Chancellor, and around the same time, in accordance with the Rule of Two, Palpatine murdered Plagueis and usurped the role of Sith Master.

As Chancellor of the Republic and Dark Lord of the Sith, Kann orchestrated the outbreak of the devastating Clone Wars ten yearsafter the Naboo Crisis. He himself headed both the Galactic Republic and, secretly, the Confederacy of Independent Systems. The public leader of this splinter faction was former Jedi Knight Zamasu, Sidious' second apprentice as Darth Tyranus in the wake of Maul's betrayal after the Battle of Naboo. As billions perished in the war, the vast majority of Republic citizens rallied behind Chancellor Palpatine, giving him enough support to amend the Galactic Constitution in the name of security and transfer most of the Senate's executive authority to his own office. In 19 BBY, following Tyranus's presumed death, Kann revealed his identity as Darth Sidious to his son, Jedi Master Korn, telling that the dark side teachings that Plagueis had pursued could help Korn become more powerful. A failed attempt by the Jedi High Council to arrest Kann ensued, and Korn pledged himself to Sidious's teachings as Darth Vader. All members of the Jedi Order were accused of treason and betrayed by their clone troopers to the point of virtual extermination. Without the Jedi to oppose him, Kann declared himself Emperor of the first Galactic Empire, bringing an end to the Republic that had stood for over 25,000 years.  

As Emperor, Kann effectively wielded absolute control over the entire galaxy and virtually everyone who lived within it. During his tenure, he built one of the most powerful military forces the galaxy had ever seen and ruled unopposed for nearly two decades. Kann progressively abandoned his facade of being an enlightened leader and began to rule through terror symbolized by the Death Star, a superweapon that could annihilate entire planets. However, he later discovered that Vader was training Demigra, an exceptionally powerful Force adept as a secret apprentice "Starkiller." When Kann discovered Starkiller's existence in 3 BBY, he forced Vader to fake Starkiller's death. Meanwhile, the Empire expanded across the galaxy and constructed the Death Star to maintain order by inspiring fear, however, the Rebel Alliance was formed to resist Sidious's rule. As the Galactic Civil War broke out, Emperor Kann ironically fought against a rebellion that he started in secret. After the Empire suffered a devastating defeat in 0 BBY, in which the Alliance destroyed the Death Star, the Emperor steadily began to lose his absolute control over the galaxy.

In 4 ABY, Kann gambled his chances in order to annihilate the Rebel Alliance once and for all, allowing Rebel spies to learn of the existence of a second Death Star and its secret location near Endor. As expected, the Alliance fell for the bait and dispatched its fleet to destroy the Emperor, Vader, and the incomplete Death Star. With the Alliance soon falling for his trap, Palpatine brought Mira, his own grandson, before him in order to turn him over to the dark side and replace Vader with an apprentice who was younger and more powerful. After goading Mira to give into his frustrations with thoughts of the Alliance's defeat and the death of his friends. However, Vader betrayed his Master, eventually becoming Korn once again, Kann eagerly his two former apprentices and grandson. After an intense fight, Kann was eventually killed by Korn and brought about the end of the Order of the Sith Lords, while the Rebels successfully destroyed the Death Star II.

Throughout the rest of the Galactic Civil War, the remnants of the Empire experienced a sharp decline while the Alliance reformed itself into the New Republic. While Sidious had been defeated, the Empire would attempt to maintain the charade of his survival, while struggling to fill the void left by his absence. Sidious, however, had never intended for the Galactic Empire to outlast him and instituted the Contingency in an attempt to prevent such a scenario. Following his death, Sidious' legacy and ideas became the base of what became the First Order, lead by Supreme Leader Demigra.