New Sith Empire (Rise of the Sith)

The New Sith Empire, formally called the Final order, was a empire reestablishing the Sith Order within the galaxy ruled formally by Emperor Sheev Palpatine who was killed and replaced by his granddaughter Rey Palpatine with the aid of three ancient sith lords. The New Sith Empire quickly expanded its territories seizing control over former First Order worlds and conquering new worlds in an effort to promote peace in the galaxy.

Rey Papalatine discovered a Rakatna device on the Infinite Empire's homeworld. Sending Darth N'lia the device was accidentally reactivated teleporting the entire Sith Empire into the past during the Clone wars. The New Sith Empire though remained hidden until their discovery by Jedi Master Obi-Wan Kenobi and his padawan Anakin Skywalker. Rey met with them and surprised them with her knowledge of who they were. Secretly Rey wanted to remove her grandfather Supreme Chancellor Sheev  Palpatine, and restore the Sith Empire fully preventing the Galactic Civil War, while preserving the Galactic Republic which would keep the galaxy locked forever and once again in sith-Jedi conflicts and a Cold War between the Republic and Sith.

The Jedi wanted to invade the Empire, but Palpatine pointed out that they would be engaged on three fronts and they don't know enough about this new sith Empire. Obi-Wan and Anakin revealed they had free reign on the Sith Capital of Exegol, but were escorted and watched over constantly by Sith and Stormtroopers, despite this they revealed the New Sith Empire had a massive fleet, and a huge army and the Sith were active in large numbers. And the Sith had advanced technology and were masters of the Dark side.

The New Sith Empire attacked the planet of Varxious which was close to the New Sith Empire's borders, stating that the planet was too close for comfort and the rogue clone army could be used by the CIS to invade the Sith. The Sith overwhelmed and destroyed the confederates replacing the ruling monarch and prime minister with a Pro-Sith backed monarch and prime minister. Varxious joined the Sith Empire, which lead to the Sith formally declaring war on the Confederacy of Independent Systems a month later. However this was a rouse Rey wanted the Sith to destroy her grandfather whom she knew was leading both fractions and the Clone Wars was part of his master plan to destroy the Jedi.

Conquest of the galaxy
Under Rey, the New Sith Empire quickly and brutally subjecting former New Republic and First Order worlds. The Resistance was unable to resist the Sith External Army and Navy. Eventually the Sith conquered much of the galaxy and pushed the Resistance toward the Core worlds. Around 43 ABY, the Sith discovered a ancient Infinite Empire superweapon on Rakatna Prime. The weapon was activated and revealed to be a teleportation device allowing an entire fleet, empire, or army to teleported to different points in time.

The Sith Empire was teleported back in time during the clone wars.