In 355.M41 the Ghosts of Retribution agent Xyptus contacted a small group of five Arbitrators for information regarding the whereabouts of the missing Lord Admiral Tyrel Hagen. The Arbitrators led the chapter to the Cult of Mourning and the Lord Admiral, and so Chapter Master decided to hire them on a full time basis. After a brief conversation Xyptus convinced the Arbitrators to enter the chapter's employ and - using the wealth of the chapter and the Arbitrators contacts - secured ten more along with additional equipment.
Following their employment to the Chapter, Reo Hestrom joined them.
In late 355.M41 Punisher Squad delved into the underhives of Hive Babelion on Tachion Primaris to explore the beacon set up by Brother Cagirates. The Arbitrators fought off an attack by a large swarm of mutants on the way down before finding the Space Marine and teleporting out with him to the orbiting Gothic-class cruiser Vorpal.
Punisher Squad consists of 1 Sergeant, 2 Senior Arbitrators, 3 Cyber-Mastiff Handlers with Cyberdogs, 10 Arbitrators and 1 Skullprobe.
- Arbitrator Sergeant Argus Verhoff - The leader of Punisher Squad. Argus Verhoff is an exceptionally tough man and a long time veteran of the Adeptus Arbites.
- Senior Arbitrator Reo Hestrom - First an Arbitrator, then an Inquisitorial Enforcer, now an agent of the Chapter. Reo Hestrom has seen it all and done it all in the name of the Emperor.
- Senior Arbitrator Devlin Stark - One of Verhoff's oldest friends. Stark is a very streetsmart and cunning Arbitrator who has experience working undercover.
- Cyber-Mastiff Handler Jameson Twill and Skullchomper - Experienced fugitive hunters. Skullchomper did not earn his name lightly.
- Cyber-Mastiff Handler Anders Bronse and Buttercup - Expert crime scene examiners, Buttercup is modified to be able to detect tiny traces of substances and DNA.
- Cyber-Mastiff Handler Klaus Frömm and Kaiser - Veterans of the street, Frömm is an older man with a vast wealth of experience.
- Arbitrator Morgan Stahl - An exceptionally large man who prefers to wear supplementary riot armour and totes a massive ceramite Lockshield.
- Arbitrator Alicia Braxen - An expert markswoman who uses a Resolution-pattern sniper rifle. Braxen is also adept at infiltration & espionage as her relatively sleight appearance does not arouse suspicion.
- Arbitrator Nelson Dominasta - Dominasta was once toted as a potential Judge thanks to his intelligence and encyclopedic knowledge of the law, but his devotion to patrolling the streets won out.
- Arbitrator Artorion Fleck - A former Slate-Agent. Fleck has undercover experience and can keep his cool in any situation.
- Arbitrator Harald Dusker - A reliable, by the books street Arbitrator who can supposedly arrest anything. Most notable was his successful apprehension of a frightened Ogryn.
- Arbitrator Xander Lawson - A breaching expert, Lawson is well-versed in all types of demolition, explosives and unconventional entry.
- Arbitrator Carmen Santago - A tough street Arbiter, Santago is an uncommonly large & strong woman and highly skilled with both shotgun and stun maul.
- Arbitrator Ranlo Grams - A skilled armourer, Grams' highly customised automatic shotgun is loaded with frag shells which - though rarely unleashed - cause mass destruction when used.
- Arbitrator Caige Barrington - Though Barrington is as skilled in combat as any street Arbiter his real skill lies in vehicle operation, and he can pilot any common-use Imperial vehicle from autotrucks to valkyries.
- Arbitrator Mylo Trosky - A young Arbitrator as well as a minor adept of the Adeptus Mechanicus. Trosky is highly skilled at interacting with machine spirits of all kinds, bending them to his will to bypass security systems, deactivate automated defences and falsify records.
- Skullprobe Blinky - Equipped with wide-band visual & auditory sensors, an advanced data core, grav suspensors, multi-tools and even a laspistol, Blinky is a useful tool for Punisher Squad.
- Arbites Carapace - Standard issue for all members of Punisher Squad. This armour is thick, imposing and utilitarian. The helmet features a sealed rebreather mounting, photon flash resistant visor and inbuilt microbead, while the magnetic belt holds a rebreather, manacles, ammunition, grenades, a pistol and a power maul. A large mag strip on the back of the armour can hold a single basic weapon, freeing the Arbitrators hands.
- Lockshield - Lockshields are massive, rectangular shields of ceramite with an armourglass viewport and firing port. They are used for shielding Arbites during heavy riots and combat and can stop a bullet dead. They also have magnetic edges, so a line of Arbitrators can 'lock' their shields into a solid wall.
- Bolt Pistol - The Ghosts of Retribution upgraded each Arbitrators standard sidearm to this potent weapon.
- Webber - Commonly issued to Arbitrators for non-lethal takedown purposes, Web Pistols and Web Guns launch a mass of sticky polymer filaments which engulf the target on impact. The targets are quickly entangled and any attempts to escape merely cause the Web to constrict further.
- Power Maul - Carried by all Arbitrators and capable of two settings. The standard setting keeps the power field engaged and makes the maul a potent weapon able to shatter flak armour, flesh and bone. The alternate setting drastically lowers the power and serves as an excellent incapacitation tool, the shock field causing muscles to spasm and lock up.
- Arbites Combat Shotgun - A versatile, powerful and reliable weapon, the Combat Shotguns only real drawback is its relatively short range (though this can be mitigated somewhat with certain shells). Typical alternate shells include stunning capacitor shells, armour-piercing slug shells, and the rare but utterly lethal exeuctioner shells that home in on their target. All Arbitrators have access to this weapon though some may choose alternate primary weapons.
- Resolution-pattern Sniper Rifle - This large semi-automatic sniper rifle is chambered in the same calibre as the famous Heavy Stubber, fed from a five-round box, and in the hands of a skilled marksman the damage of each round can far exceed even their usual potential.