The Blackguards were a covert division of the Pijal Royal Guard introduced in the canon Star Wars novel Master & Apprentice.
The group was commissioned by Crown Princess Fanry, who was to take the throne in a reformed monarchy where the monarch no longer had absolute power but was instead was a constitutional monarchy with a democratic assembly. The group carried out a series of bombings and other terrorist attacks on various Pijali targets. The government was quick to pin the Blackguards attacks on Pijali opposed to the government, especially as it sought to sign a diplomatic treaty with the Republic that would largely give Czerka Corporation control of the system. The attacks also served to distract the Jedi regent Rael Averross and keep him from sensing what was really going on. Fanry's Royal Guard Captain Deren was aware of the Blackguards. He wanted nothing to do with them but felt duty bound to support Fanry and the Blackguards.
At Fanry's coronation she stabbed the official administering the oath of office and then had the Blackguards attack to buy her time to escape to her flagship. Fanry was quickly deposed when her aide Cady realized that Fanry didn't care about the Czerka slaves or taking care of her people, but her own power.
The realization that Fanry had commissioned the Blackguards and authorized them to carry out terrorist attacks along with her violent behavior at the coronation turned the Pijali against Fanry, and she was forced to step down as Queen. In the aftermath the Blackguards were disbanded as the monarchy was abolished in favor of a democratic government, which signed a more equitable treaty with the Republic.