Palpatine was a Force-sensitive human male who ruled both as the Dark Lord of the Sith as well as the Emperor of the Galactic Empire from 19 BBY to 4 ABY. Palpatine is recorded by history as the most successful Sith Lord who had ever lived, with his deeds resulting in the overthrow of the Old Republic and the near extinction of the Old Jedi Order, destroying both from within, using his power as Supreme Chancellor of the Galactic Senate to manipulate its members into calling for the destruction of the Jedi.
Noted for his sadistic and self-serving intentions just as well as his ability to conceal them, Palpatine impacted the Galaxy perhaps more than any other single individual, and it is likely that his impact on history, for good or ill, is immeasurable.
His rise to evil began at a young age, when Palpatine began collecting discarded Sith artefacts, feeling his own connection to the Force drawing him to them. His connection to the Force would cause him to meet a traveller named Damask, who revealed himself as a Sith Lord. Eager to train under him, Palpatine killed his own father, proving to Damask that he was worthy of training under the Dark Side.
- Palpatine lived a double life for many years, successfully concealing his identity as a Sith. He served an untarnished career as a senator of the Old Republic, representing his home planet Naboo.
- 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 Bane's Rule of Two, Sidious murdered Plagueis and usurped the role of Sith Master.
- As Chancellor of the Republic and Dark Lord of the Sith, Palpatine orchestrated the outbreak of the devastating Clone Wars ten years after 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 Master Count Dooku, Sidious' second apprentice as Darth Tyranus in the wake of Maul's presumed death on 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' demise, Palpatine revealed his identity as Darth Sidious to the Jedi Knight Anakin Skywalker, telling that the dark side teachings that Plagueis had pursued could help Skywalker to save his wife, whom Skywalker had foreseen dying untimely. A failed attempt by the Jedi High Council to arrest Palpatine ensued, and Skywalker pledged himself to Sidious' 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, Palpatine declared himself Emperor of the first Galactic Empire, bringing an end to the Republic that had stood for over 25,000 years.
- As Emperor, Palpatine 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. Palpatine 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 Galen Marek, an exceptionally powerful Force adept as a secret apprentice "Starkiller." When Palpatine discovered Starkiller's existence in 3 BBY, he ordered Vader to fake Starkiller's death and then request that Starkiller assemble the most influential traitors in the Empire in a rebellion in order to highlight and destroy them all. Palpatine's plan backfired when Starkiller, healed from his near-fatal injuries and espousing the teachings of the light side, vowed revenge against Palpatine and confronted him on the Death Star, ultimately sacrificing himself in an act that inspired the dissident senators to create the Alliance to Restore the Republic. As the Galactic Civil War broke out, Emperor Palpatine 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, Palpatine 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, Sidious brought Luke Skywalker, the son of Darth Vader, 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 Skywalker to give into his frustrations with thoughts of the Alliance's defeat and the death of his friends, the Dark Lord eagerly watched as father and son fought one another. However, Skywalker refused to submit to the dark side and spared his father, prompting Sidious to unleash all of his rage and hatred on Skywalker. Unwilling to stand by and watch his son die from the agonizing effects of Sidious' Force lightning, Vader finally redeemed himself, throwing his astonished Master down the Death Star's shaft, a sacrifice that fulfilled the prophecy of the Chosen One and brought about the end of the Order of the Sith Lords.
- 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. However, Sidious did not stay dead, and eventually used a rare and ancient Force technique to transfer his spirit into one of many clone bodies stored on the Deep Core world of Byss. In 10 ABY, Emperor Palpatine resurfaced in the galaxy in a bid to rebuild his Empire, temporarily converting Luke Skywalker to the dark side and installing him as his apprentice. Sidious' efforts to live forever, however, were undermined by subversives within his own inner circle, including his Royal Guard Carnor Jax. With the last supplies of healthy clone bodies sabotaged and their genetic source material contaminated by his allies, Palpatine desperately tried to take over the body of Darth Vader's youngest grandchild, the infant Anakin Solo, in 11 ABY. Sidious' spirit, however, was intercepted by the dying Jedi Knight Empatojayos Brand, who dragged the Sith Lord down into the depths of the Force forever, though his legacy continued to live for countless years.