Purge troopers were large in stature, standing at twice the height of an average humanoid. Designed to combat Force-users, their primary offensive weapon was an energy blade extending from their left forearm, along with a shield to block attacks. In addition, the droids were outfitted with Duranium armor enhanced with refined cortosis which reduced the damage dealt by lightsaber attacks.
Purge troopers also boasted a high-powered, medium-ranged rocket launcher providing them with a means of ranged attack, as well as magnetic tractor boots which made them resistant against being gripped or pushed with the Force-based telekinesis. The missile launcher was present on their right shoulder.
The one weakness these droids had in terms of Force-based abilities was Force lightning, which was an exploitable vulnerability.
Originally conceived by a Techno Union engineer trying to devise a more effective means to fight Jedi Generals, the plans for his design were retrieved by clone commandos after a raid on his facility killed him. The purge trooper was finalized by an Imperial Intelligence research and development team who commissioned the creation of a wide range of advanced battle droids. The resultant purge troopers were created with the specific purpose of fighting against surviving Jedi and other Force users.
Warning: The following section is non-canon. It contains information explicitly released under the Infinities brand, and/or confirmed to be non-canon by the author or Lucasfilm. Everything said in this section and not elsewhere did not happen in the "proper" Star Wars continuity.
In the year 0 BBY of an alternate timeline, Jabba the Hutt kept a small number of old and reprogrammed purge troopers in his palace on the planetTatooine. When LordStarkiller, EmperorPalpatine's apprentice and personal assassin, sought an audience with the Hutt criminal, Jabba ordered his henchmen to kill the Dark Lord. As Starkiller navigated his way out of the palace, he was confronted by two purge troopers, both of which he destroyed before proceeding to Mos Eisley.