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"Knowledge is half the battle."

— Saying of the Mentors Chapter

The Mentors, sometimes referred to in Imperial records as the Mentor Legion, is a Loyalist Codex Astartes-compliant Space Marine Chapter. The Mentors were raised during the 26th Founding in 738.M41, making it one of the most recently founded Chapters in the Imperium of Man.

The Mentors are known to be a reclusive and suspicious Chapter of Astartes who no longer trust other Space Marine Chapters or the Imperial government, preferring to work alone and unobserved by all save the foes of Mankind and the Emperor.

Some -- highly unreliable and apocryphal -- fragmentary records suggest that the Chapter has at times fielded warriors of unusual size, strength and fortitude.

Imperial records indicate that companies of the Mentors are currently engaged against the Aeldari of the Biel-Tan Craftworld as well as the Orks of the Charadon System.

Since the opening of the Great Rift, the Mentors have received an infusion of Primaris Space Marines. They have gained the necessary knowledge and technology to create new Primaris Astartes and to help their less advanced Firstborn brethren ascend to the new status by undertaking the dangerous surgery required by the Rubicon Primaris.

Chapter History

Mentors Chapter Colour Scheme as displayed by a Firstborn Space Marine Sergeant of the 3rd Company, 3rd Tactical Squad; the helmet stripe's colour designates company.

Often referred to as the "Mentor Legion" in older Imperial records, the Mentors is a 26th Founding Chapter created in 738.M41 and is the second Chapter of Astartes to be designated number 888 (the first being the now-lost Star Scorpions).

This came about because the Star Scorpions, a Chapter created during the 25th Founding, suffered from both the misfortune of producing redundant gene-seed and of becoming lost in the Warp and being utterly devastated by very powerful Warp entities. Some of its company eventually returned to Imperial space after the opening of the Great Rift as the warband of Heretic Astartes known as The Pure.

Though the Star Scorpions' ultimate fate remains unknown to the Imperium, the High Lords of Terra, acting in the name of the Emperor, declared the Chapter lost.

Mentors Chapter Colour Scheme as displayed by a Primaris Marine. The Mentors denote company by helm colour; this Battle-Brother belongs to the Chapter's 4th Company.

While stocks of the Star Scorpions' gene-seed had survived the loss of the Chapter, the high rate of mutation found within it made it useless when the Adeptus Mechanicus moved to try to reconstitute the Chapter, and eventually the Magi Biologis and their chem-architects were forced to concede defeat.

For a time it seemed that Chapter Number 888 would never be raised again, but some years later, with a new Founding in the offing, the Mechanicus was persuaded to revisit the Chapter regalia. Thus, during the 26th Founding, the Mentors Chapter was born.

It received the Chapter colours and number of the extinct Chapter but instead of the Star Scorpions' redundant gene-seed, it was granted an entirely new generation of Astartes genetic material collected from the storage banks of Terra's gene-laboratories.

Notable Campaigns

  • Golance War (987.M41) - The Flesh Eaters Force Commander Isiah was in charge of the campaign on the world of Golance to prosecute a war against encroaching Aeldari. Unable, after numerous attacks, to rid the planet of the troublesome xenos who had gained control of the world's secret arsenal, the Chapter was at its lowest ebb, having suffered the loss of 350 men and officers at the hands of the manipulative and treacherous Aeldari. The Flesh Eaters finally received relief in the form of five Astartes of unparalleled skill from the Mentor Legion to deal with the vile Aeldari scum and change the course of the war.
  • Biel-Tan (Unknown Date.M41) - Imperial records indicate that elements of the Mentors Chapter are currently engaged against the Aeldari of the Biel-Tan Craftworld.
  • Battle of Charadon (Unknown Date.M41) - Several whole companies of the Chapter are currently deployed alongside the Imperial forces engaged against the massive Ork WAAAGH! in the Charadon System.
  • Unforgivable Theft (Unknown Date.M41) - Illuminor Szeras led his Necron legion of the Sautekh Dynasty in an attack upon the Imperial world of Gorszt, destroying a fortress complex belonging to the Mentors Space Marine Chapter. As his prize, Szeras claimed the entire stock of precious gene-seed that lay hidden beneath the fortress.
  • The Humbling (Unknown Date.M41) - Endt Thrinn, the genius Planetary Governor of the world of Inviolus, completed his dynasty's planet-girdling fortress network. In his cups, he was much given to boast that his home planet is unassailable. Agents of the Alpha Legion relayed this claim to their Iron Warriors brothers, and before long the Chaos Lord Mandrakk had made Warp translation in-system at the head of a large fleet. Instead of attacking Inviolus directly, he invaded the nearby Agri-World of Dalathro's Rest. The bread basket of the Inviolus System, Dalathro's Rest was well-defended by the Astra Militarum. Mandrakk bombarded it from orbit whilst launching boarding actions against every craft bound for Inviolus. Within a Terran year the people of Inviolus were crippled by starvation. Though reinforcement arrived in the form of a company of Mentor Legion Space Marines, Mandrakk had ensured that Inviolus' half-starved defence forces were easy prey for his teleporting annihilation squads. The planet was ultimately seized and repurposed as a Chaos base.

Chapter Organisation

The Mentors Chapter is roughly organised in much the same fashion as the Ultramarines. However, the bulk of the Chapter is never seen by outsiders as the location of its homeworld and fortress-monastery is an absolute secret.

Only the very highest Tech-priests within the hierarchy of the Adeptus Mechanicus are aware of its exact location. It is within that hidden location that the Mentors perform their rigorous training and disciplining.

The massed ranks of the Chapter are exhaustively trained in the art of war and in the use of Imperial military hardware, both old and new, as the Chapter's primary purpose is to act as a test-bed for the latest Imperial military technology developed by the Mechanicus.

While a large proportion of the Chapter's Astartes are permanently based at their secret headquarters, the balance of the Chapter is sent out on missions intended to shore up weak points in the Imperium of Man's defences.

The Mentors also deploy their battle-brothers primarily as one of two special formations, as described below.


The typical Mentors squad is organised around the archetypical Codex Astartes-approved ten-man-squad. In addition, the Mentors uphold the tradition of splitting into two groups of five battle-brothers each when in battle.

Each of the ten men in the squad is a Veteran battle-brother known as a "Tutor." There is no acting sergeant in charge of the squad, as each Space Marine holds the same rank and any of the ten may be nominated to lead, or two leaders may be selected if the squad is split into the two, five-man squad formation.

Elite Cadre

Another facet of the Mentors is the development and training of the Chapter's Elite Cadre. It was originally envisaged that these specialists would perform a number of important semi-military roles, from counter-terrorist operations to undertaking complex undercover special forces missions.

The Elite Cadres of the Mentors Chapter are the most advanced warriors of their kind within the Adeptus Astartes. They are usually deployed to achieve highly specialised military objectives that would normally be considered the role of special operations troops or commandos in other forces, such as counterterrorism, demolitions, infiltration and reconnaissance deep in enemy territory.

Elite Cadre members expect to be deployed to deal with threats that lie outside the scope of a Space Marine Chapter's standard tactical doctrines, much like a Deathwatch Kill-team. When squads of the Elite Cadre are deployed to aid Imperial Commanders across the galaxy, they are either used as traditional special operations troops to carry out crucial missions that other warriors cannot or they are broken up, with each Astartes used as a force multiplier by becoming the commander of an individual unit of frontline combat troops.

They serve as the Imperium's ultimate special operations warriors, intended to be capable of dealing with any threat outside a normal Chapter's expertise, though this aim has not been fully realised as yet. Each member of the Elite Cadre is a formidable senior Veteran Battle-Brother of the vaunted 1st Company.

These members represent the pinnacle of their Chapter's success to date. There are distinctly fewer Elite Cadre Astartes within the Chapter than normal Mentors battle-brothers, but what they lack in numbers they compensate for in sheer power, skill and application of advanced hardware.

Those chosen to become a part of the Elite Cadre are selected due to their advanced training, adaptability in battle and lateral thinking in strategic and tactical acumen. Elite Cadre Astartes seconded to other Imperial forces are often employed as squad leaders as they make especially effective commanders of Astra Militarum or Planetary Defence Forces units.

The Elite Cadres are also frequently called upon by the Inquisition which recognises their superior skill at arms. The Mentors are known to second their Elite Cadre members to other Space Marines Chapters allied with them, where their expert guidance and mastery of the military sciences enable other Astartes to achieve a unique level of knowledge and skills that will help them spread the light of the Emperor to the darkest corners of the galaxy.

The Elite Cadres are also used by the Adeptus Terra for a variety of small-scale special operations that call for the deployment of a small group of elite troops rather than the conspicuous might of an entire Space Marine force.

Chapter Combat Doctrine

"One war, one Cadre."

—Nisk Ran-Thawll

The Mentors Chapter is highly unusual amongst its fellow Space Marines and its modus operandi is quite different from that of the bulk of the Adeptus Astartes. The Mentors do not fight as a single force or even usually as full companies but instead second squads drawn from the Chapter's companies to supplement other Imperial military forces.

This is because one of the unusual traits of Mentors Astartes, which may derive from an unforeseen mutation within their gene-seed, is that every Mentor possesses a near-genius ability to observe, memorise and adapt to any situation.

This extraordinary capacity for learning is especially true in all matters military. The Chapter's main pursuit is therefore one of perfecting the fusion between the fruits of military science and the art of war. This extraordinary boon means that every Mentors Astartes is the equivalent of a professor of military science and military history with many standard years of combat experience.

As a result, squads of Mentors Space Marines can serve as force multipliers when they are embedded in other Imperial military forces, such as with the regiments of the Astra Militarum or the starship squadrons of the Imperial Navy. Mentors Space Marines are thus deployed at the request of the various Imperial Segmentum Commands all across the galaxy wherever their particular talents would prove to be most useful.

The basic rationale behind seconding Mentors Squads to other Imperial Adepta is that the Mentors are able to extract the maximum amount of information regarding the fighting prowess and techniques of just about any Imperial military force and thus how to improve their operational efficiency. When these squads return to their Chapter headquarters they bring with them an invaluable record which is without parallel in the galaxy.

Other Space Marine Chapters and Astra Militarum regiments to whom these squads are sent benefit from having these superior warriors join them for a campaign or battle. An extra benefit to the Mentors of this operational structure is that they are able to claim and maintain an honourable record of real combat experience despite their focus on training and research and development. As a result of this uniquely varied combat record, the Mentors have added enough citations to their Roll of Honour to make far more venerable Chapters envious.

The most experienced and skilled Mentors Astartes are Veterans who belong to a special unit somewhat similar to standard Chapters' elite 1st Companies that is known as the Elite Cadre. The Astartes of the Mentors' Elite Cadre are some of the most skilled warriors to have ever operated in the galaxy. Elite Cadre members expect to be deployed to deal with threats that lie outside the scope of a Space Marine Chapter's standard tactical doctrines.

The Mentors are based in a highly-secret fortress-monastery complex that is located on a classified world. Most of the Chapter remains within this complex at any one time, constantly training and distilling down to its essence all of the military knowledge they have gained. Select squads are chosen to leave and carry out missions for the Emperor and the competition is intense within the Chapter to be chosen for these excursions.

The Mentors Chapter enjoys close links with the Adeptus Mechanicus, and is known to be unusually technologically innovative in its own right. The Chapter also acts as a test bed for new Imperial technology recently developed by the Mechanicus. Consequently, the Mentors' equipment is of a superior standard in terms of reliability and technical complexity to that of the average Space Marine Chapter, if such a thing can be said to exist.

Deathwatch Service

The Mentors prefer to work alone, even when seconded to the Deathwatch. For this reason its battle-brothers often volunteer for one-man combat duties that aid their Kill Team's mission from a distance.

Notable Mentors

The Mentors' Chapter Master Nisk Ran-Thawll.

  • Chapter Master Nisk Ran-Thawll - The Chapter Master of the Mentors, Nisk Ran-Thawll, is one of the most formidable Space Marine commanders within the Adeptus Astartes, for he has the authority to refuse field testing of any new wargear thought to be dangerously unstable. There is no record of Ran-Thawll ever choosing to exercise his veto. He is thought to have visited Terra several times and is rumoured to have been granted an audience with the Emperor of Mankind Himself, though the reason remains unknown.
  • Manse Jah-Hlley - A Tutor of the Mentors Chapter. Jah-Hlley was instrumental in training the imperial citizens to become a militant cadre, which would bring down the renegade aristocracy that had taken over Khost Hive.
  • Lieutenant Commander Amadeus Kalus Incarius - In the wake of the Great Rift's birth, Amadeus Kalus Incarius was sent to the region of Elara's Veil to determine if the Space Marine Chapters protecting that portion of the Emperor's realm -- the Emperor's Spears and the Celestial Lions -- remained loyal. In the course of aiding the Emperor's Spears in fighting off the forces of the Chaos Space Marine warband known as The Pure and their horde of Exilarchy Chaos Cultists and mutants, Incarius was so badly wounded that his body would have needed to be largely replaced with bionics. To save his life, he instead underwent the transformation wrought by the Rubicon Primaris, and became a Primaris Marine. In the end, learning that the Inquisition was still pursuing a vendetta against the Celestial Lions Chapter and that the Warp Storms of the Great Rift had cut Elara's Veil off from the rest of the galaxy, Incarius chose to join the Emperor's Spears Chapter. He took the name Vadhán or "False Scorpion" in the dialect of the Vargantes tribe of the Emperor's Spears' homeworld of Nemeton. The name was chosen for him because the Mentors had taken on the colours and Chapter number of the Star Scorpions, the Emperor's Spears' former allies.

Non-Astartes Personnel

Aduradha Daaz, helot of the Mentors Chapter

  • Anuradha Daaz (Helot) - Anuradha Daaz was a helot, or Chapter serf, in service to the Mentors Chapter. She accompanied Lieutenant Commander Amadeus Kalus Incarius on his mission into Elara's Veil and played a major role during the events in which her master helped to save that Chapter from the machinations of the Exilarchy and The Pure. Daaz followed Incarius into service with the Emperor's Spears Chapter and served both well into her old age.

Chapter Fleet

Chapter Relics

  • Ran-Thawll's Gaze - Ran-Thawll's Gaze is a highly advanced Auspex with several unique functionalities. Its detection range is extended out to a kilometre. Furthermore, materials that would normally inhibit or block Auspex scans do no restrict Ran-Thawll's Gaze. The Omega Vault yielded up this unique Auspex upon the arrival of a Battle-Brother of the Mentors Chapter to Watch Fortress Erioch several centuries ago. The warrior is said to have simply approached the opening doors and taken the relic as if he had been expecting it, although this may be simply another legend surrounding his secretive Chapter and its obsessive mastery of knowledge.

Chapter Appearance

Chapter Colours

The Mentors' primarily wear dark green power armour, which includes the power pack, helm, torso and shoulder plate trim.

The shoulder plates, arms and legs are white. The red squad specialty symbol -- battleline, close support, fire support, Veteran or command -- is located on the right shoulder plate.

A black High Gothic numeral is stenciled on the centre of the squad specialty symbol, which indicates squad number.

The colour of the helmet indicates company number in accordance with the Codex Astartes -- i.e. White (1st Company), Yellow (2nd Company), Red (3rd Company), Green (4th Company), etc.

Chapter Badge

The Mentors' Chapter badge was originally the stylised face of an owl, but was later changed to that of a profile of a stylised red raptor's head, centred on a field of white.

Canon Conflict

In the novel Spear of the Emperor by Aaron Dembski-Bowden it is revealed that the Mentors are a Successor Chapter of the Ultramarines.

However, in the more recent revised 8th Edition Codex: Space Marines, the Mentors are once more listed as a Chapter derived from an unknown Founding.


  • Adeptus Astartes: Successor Chapters (Limited Release Booklet)
  • Codex: Necrons (8th Edition), pg. 31
  • Codex Adeptus Astartes - Space Marines (8th Edition), pg. 58
  • Codex Adeptus Astartes - Deathwatch (7th Edition), pg. 21
  • Codex Heretic Astartes - Chaos Space Marines (8th Edition), pg. 32
  • Codex: Space Marines (8th Edition) (Revised Codex), pg. 58
  • Codex: Space Marines (6th Edition), pg. 73
  • Codex: Space Marines (5th Edition), pg. 29
  • How to Paint Space Marines, pg. 86
  • Deathwatch - Honour the Chapter (RPG), pg. 131
  • Warhammer 40,000 Compendium (1st Edition), pp. 4-5
  • White Dwarf 98 (UK), "Index Astartes-The Mentor Legion" by Bryan Ansell, Alan Merrett and Paul Cockburn, pp. 39-44
  • Angels of Death: Cadre (Short Story) by Josh Reynolds
  • Spear of the Emperor (Novel) by Aaron Dembski-Bowden, Chs. I, II, IV, VIII, XVII, XX