The Black Guard were a plain-clothes police force set up by Darth Micail in the year 61 ABY. Originally created to keep order on many of the newly conquered worlds, they quickly gained a reputation for their ruthlessness.
They received their nickname, the Black Guard's due to their tendency to wear all black, making them feared opponents of crime.
By the year 180 ABY the Black Guard were the second largest military force in the galaxy, after the Sith troopers, and were responsible for the security of thousands of worlds; including Coruscant, Naboo, Sith'ika and Nerezza.
Following the destruction of the Chemical Vats on Anzat during the Octom War the Black Guard were made responsible for dealing with the upsurge in rebellious activities that were taking place throughout the galaxy.
The Black Guard were key in the defeat of the Coruscant rebels during the Coruscanti plague, arresting thousands during the rebellion, including Salis and Salis Pénzember, Jr.
