The Holy Sith Empire, or Galactic Sith Empire was an empire founded by Darth Sidious.
Drawing from the structure if Darth Revan and Emperor Vitiate in which there was one leader and many underlings beneath him.
It's history lies as the imagination of a young Palpatine under the tutelage of Darth Plagueis. As a senator and later Chancellor Palpatine saw the time of his empire grow. Palpatine would travel the galaxy recruiting various dark jedi to be his Sith Lords and even appointed 12 of the most powerful to be members of the sith council. In 19bby Palpatine turned the republic into the Holy Galactic Sith Empire. Despite not having Anakin as his apprentice he cloned him and dubbed the clone Darth Vader.