The Sith Empire was a large army of Anti-Republic warriors & bounty hunters during the Great Galactic War & Sith War. They utilized Sith, Imperial Soldiers, & Droids.
The Sith Empire was formed after the Great Hyperspace War. when the previous Sith Empire fell. Darth Malgus reorganized the remenants and formed the Empire. There army consisted of hundreds of loyal & unloyal troops to fight the Republic. Most of the unloyal troops were bounty hunters.