The Inquisitors have appeared in various Star Wars TV series, comics, video games and novels. Originally introduced in Star Wars Rebels, the Inquisitorius is the Empire's organization of dedicated Jedi hunters, designed to ensure the completion of the Great Jedi Purge following the initial execution of Order 66. These dark side adepts are all former Jedi themselves, who have been broken and corrupted by the Empire.
Source:https://www.cbr.com/star-wars-inquisitorius-creation-explained/