Consul

Legiones Consularis, or Consuls, were a rank bestowed to Space Marines during the Great Crusade and Horus Heresy. They were not Legion Consuls, which were specifically tasked with keeping order in the Legions. They were identified by their specialization in many esoteric arts of combat and war. Called upon to use their mastered arts when their Legion needed them, with the outbreak of the Horus Heresy these officers would face their grandest trial. As one can imagine, there is a metric shit ton of different variants of Consuls.

Variants

Consul Armistos

Where the Champion is a master of blades, the Armistos is a master of firepower, the bigger the better. Usually assisted by masters of the armory, the Armistos is constantly testing the most cutting-edge firearms in order to find the finest to deliver death from afar.

In the Horus Heresy tabletop, the Armistos gains hardened armour to protect themselves from blasts as well as a Cognis Signum. Most notably, they gain access to an array of master-crafted heavy weapons, allowing them to make the most with their heaviest guns.

Consul Castellan

Of the VII Legion, the Castellans were strict enforcers, honing the firing drills to perfection. When they leave a world, they only leave behind a compliant fortress, staffed by loyal soldiers.

The Castellans are a new addition to the Liber Astartes in the reboot Horus Heresy tabletop. Similar to the Armistos, they get hardened armour and a heavy weapon - though their options are restricted to the heavy bolter, autocannon, and the legion-exclusive Iliastus Assault Cannon.

Consul Champion

The predecessor to the Company and Chapter Champions of the Chapters, their role has seen the least amount of change. After all, the Champion was always meant to be an exemplary swordsman among their brothers and fight the greatest foes. How else were they to improve that?

Consul Chaplain

While the Imperial Cult was not established yet, there were still people who needed to shout really loudly to inspire zealous anger. Similar to their successors in black and bone, these chaplains would inspire hatred in their charges and wield a master-crafted Power Weapon - though unlike the Crozius Arcanum synonymous with the later iterations, these could be any sort of power weapons than merely mauls.

Speaker of the Dead

Before the VI Legion had Wolf Priests mixing Fenrisian Lore with the Imperial Creed, the Speakers of the Dead were the resident apothecaries-slash-cult leaders of the lesser deity Morkai.

In the tabletop, this not only gave an attached unit Hatred (Everything) and Stubborn, but they also gained a Narthecium and a master-crafted power maul in place of the Crozius they would later gain.

Consul Delegatus

In smaller conflicts where the Legion's top command would deem the situation to minor to directly intervene, they would deputize a lesser officer, typically a Centurion, with full command of their own army. These officers would then assemble their own strike forces to lead into battle.

In the tabletop game, the Delegatus is an upgrade that offers no special equipment, but it does grant the Consul the Master of the Legion rule, and thus the ability to qualify as the warlord in smaller games as well as the ability to select a Rite of War as if they were a Praetor. They also get a single-use ability to roll a Leadership Check to force any units that were falling back or pinned to rally and act normally for the turn.

Consul Forge Lord

Though trained on Mars in the ways of the Mechanicum, unlike the Praevians the Forge Lords are selected for their incredible skill with machinery. While they may have made use with the war machines of the Mechanicum, their preferences usually led them more to repairing the Legions armoured forces. As with their successors, these Forge Lords were usually the anchors to lead all the production within the legions.

On the Horus Heresy tabletop, Forge Lords were given their servo-harnesses to help them repair their vehicles as well as being useful multi-weapons. On top of this, they could also purchase Cortex Controllers, which would prove particularly useful if they also decide to ally with any automata on the field, including the Thallax maniples that they unlock access to.

Consul Herald

The forebears for the Chapter and Company Ancient, the Herald is charged with holding aloft their Legion Standards. As ever, the Legions fought with religious fervour to protect those who held these artefacts, which were usually touched by the Primarch and gifted to an officer as a sign of favor.

The tabletop represents Heralds by forcing them to sacrifice either their pistol, bolter, or combi-bolter so they could have a free hand to hold this weighty standard.

Consul Librarian

Due to the Council of Nikaea, the Librarius was dissolved among the legions, but as many can attest, this was not for long.

In most cases, there may have been cases where a Psyker was elevated to a more senior position to make use of their unnatural powers, but as time passed, it became clear that the powers of psykers were one of the only ways to defeat the foul warpspawn that the traitors summoned...or to summon them. Following the Heresy War, Guilliman would re-establish the Librarius as a structure in the Chapters.

As with their future successors, these Librarians would have access to Force Weapons with which to channel their psychic powers. Psychic Hoods did exist in this era in order to help cancel out any harmful psychic influences, but they were not so common that they could be issued to any Librarian that wanted one.

Consul Esoterist

Among the psykers of the legion, only a growing few of them dared to dive deeper into the unknown fields of Warpcraft, but it proved to be incredibly effective, if in varying ways. While the loyalist legions had Esoterists who studied how to banish daemons outright, the traitor legions discovered ways with which they could summon the forces of Neverborn into reality with their own power.

Esoterists are a specialization that only appeared with the rebooted Horus Heresy tabletop game, and by all means, they are identical to Librarians with two exceptions - one is access to Archaeotech Pistols, but the bigger one is their own unique Anathemata psychic discipline (or the Sanctic/Malefic Daemonology in the original books), which is inaccessible by any other way.

Caster of Runes

Before they were called Rune Priests, the Casters of Runes were the standing psychic force of the VI Legion. Of course, they were deemed "exceptions" to the ban on Librarians due to claiming their powers were derived from shamanism and channeling the spirit of their homeworld of Fenris.

Practically, aside from their limited choice in psychic powers (including some of their own), they were identical to Librarians.

Diabolist

Is it any surprise that these consuls hailed from the XVII Legion? Indeed, as Lorgar dove further into the Primordial Truth, so too did his sons continue diving into this forbidden lore of the daemons, even as this knowledge corrupted their souls and twisted them. One might assume them as the predecessor to the Master of Possession that would lead the Legions of Chaos, and that is quite close a guess.

In the Horus Heresy tabletop, these consuls are special psykers with force weapons who partake in forbidden daemonology, essentially becoming daemons. This will require the rest of the army to take Dark Channeling to similarly become daemons if you want the Diabolist to join a squad. Unlike the Librarian, they see no need for psychic hood.

Stormseer

Similar to the VI Legion, the Stormseers of the V Legion were also treated as special "exceptions" to the no-Librarians rule due to being shamans, though the Stormseers weren't so hypocritical as to reject the Librarius as a failed structure. These Stormseers would persist after the Heresy and effectively become the Librarius for the chapter.

Practically, aside from their limited choice in psychic powers (including some of their own), they were identical to Librarians.

Consul Moritat

Where the role of Consul is usually seen as a role of some renown and leadership, the Moritat does not get such acclaim. Being drawn from the scorned Destroyer companies, the Moritat is specially tasked to deliver death without relying on the command structure most would use.

On the Horus Heresy tabletop, the Moritat is specially noted for their rad grenades and their dual-pistol loadout, their most iconic feature as it lets them rapid fire these pistols to an almost comical degree. However, the Moritat is also unable to lead anything aside from an attached Destroyer squad.

Consul Mortificator

Among the Techmarines, the Mortificators are those who spend the most time with the honoured Dreadnoughts of the legion. As they know the most about these venerated war machines, they will accompany the dreads into the fray, constantly assuring that they operate at their finest.

On the Horus Heresy Tabletop, the Mortificator serves as the keeper of the dreads, attached to a talon of dreads despite usually being unable to. These dreads gain a Feel No Pain save on top of the consul's ability to repair dreads. The Mortificator comes equipped with a servo-arm and a Corposant Stave, an unusual archaeotech weapon that can overload enemy machinery.

Consul Pathfinder

With the extreme demand for bodies in the Heresy, there were few scout companies that were utilized as they tended to be thrown into power armour as soon as possible. As a result, the scouts of these days tended to be experts in the field, opting to the light armour for the sake of completing covert ops that the rest of the legion would not see as feasible.

In the Horus Heresy tabletop, the Pathfinder is an addition to the Liber Astartes/Hereticus books of the reboot. The Pathfinder is the only Consul equipped with Scout Armour.

Consul Praevian

In the Great Crusade. Battle bots was an actual thing.

The Consul Praevian was a type of Astartes commander during the Great Crusade and Horus Heresy and a variant of the Consul.

Trained on Mars by the Mechanicum these commanders were the keeper of the Legion's robots, including Battle-Automata given honorary induction into the Legion's ranks. On the field of battle they marched at the forefront of Battle-Automata forces, guiding them through the engagement.

They were often chosen from Veterans whose injuries required extensive Bionics. Known to be solitary individuals, they rarely advanced up the chain of command. Some Legions used the rank as a dumping ground for warriors seen as unfit for other duties. However, in the Iron Hands (No surprise there) and Salamanders, the rank was seen as a great honour. On the traitor side, Iron Warriors also make great use of them due to their command over siege robots. As they are heavily augmented, they wore what is essentially Artificer Armour for defence, but by the time of Horus' clusterfuck benanza some of them had to wear Mark V: Heresy Armour.

Some has considered viewing them as a predecessor of the Techmarine, but with each of them in command of a mini robot-army.

On the Horus Heresy tabletop, they are the Master of the Legion's Automata. He is a Support Officer, so cannot be used as a compulsory HQ and thus cannot be in an allied contingent. Comes equipped with a Cortex Controller, Cortex Designator and can't take anything that makes him bulky. First, you choose a type of Battle Automata (only Castellax and Vorax at this time) to accompany him, forming one unit with MCs (so he can't go to ground) that he can't leave. Any time the Praevian hits an enemy unit with a ranged attack, he grants Preferred Enemy to the Automata in his unit for that turn (so give him a bolter). Upgrade them with Enhanced Targeting Arrays for 2+ re-rollable accuracy for your weapons.

The original Praevians of the Forge World Black Books were unique in that they not only treated their charges as members of the legion, but they could also equip them with special equipment that might have proved useful to them.

Consul Primus Medicae

Chosen from the most senior officers of the Apothecarion, the Primus Medicae is the figure in charge of the well-being of his brothers and their gene-seeds. In those situations where they take to the field, the Primus Medicae is singularly dedicated to the safety of the Legion's health.

In the Horus Heresy tabletop, the Primus Medicae is given the Narthecium befitting their station as well as a special rule to let n attached unit re-roll any Feel No Pain saves they make from that Narthecium.

Consul Primus Nullificator

As the Heresy ground on, the Loyalists tried a great many methods to ward off the daemons. One of these would be the Nullificators, a small force of marines who adorned their power armour with Hexagrammatic Wards and used superstition and normally unsanctioned weapons like disintegrators. Leading these forces would be the Primus Nullificators, psykers who would be specially trained to purge daemons.

On the Horus Heresy tabletop, the Primus Nullificator uses these Hexagrammatic Wards to protect themselves against the warp. Alongside their guns (which could also include the disintegrator), they wield the Aether-shock Maul, a special power weapon made to demolish the daemon. Their main goal is opening extended access to the Nullificators, allowing one to field them without restriction as a Troops choice, though they got Support Squad to prevent them from scoring.

Consul Siege Breaker

When a warzone required absolute destruction, one need look no further than the Siege Breakers of the Legion. Usually leading from the front, the Siege Breaker directs their forces to demolition.

In the Horus Heresy tabletop, the Siege Breaker comes loaded to bear with a Nuncio-Vox to guide artillery and Phosphex Bombs to demonstrate that they want scorched earth. More importantly, they gain access to phosphex and chem rounds for their artillery tanks, burning whatever they strike.

Dark Emissary

Agent of the Warmaster and the XVI Legion, the Dark Emissary is dispatched to other legions, seeking to corrupt their leadership by whispering honeyed words. For those that turn from the Emperor, the Dark Emissary becomes the voice of their leader and enforcer of Horus' Will.

The Dark Emissary is a legion-exclusive consul in the HH tabletop reboot. As they are not warlords, they are instead seen only in allied detachments of the Sons of Horus. They wield the Staff of Dark Authority, a special power weapon that serves as their staff of office.

Pack Thegn

Serving the Jarls of the VI Legion's great companies, the Thegns serve as a champion with plenty of experience to impart to their troops. However, they do not view this as an honour as these Thegns have been passed up for promotion as Jarl, whether by suffering some grave dishonour or as the lone survivor of their pack.

Paladin of the Hekatonystika

The I Legion was known for its labyrinthine orders and chambers, an anomalous organization that made it impenetrable to outsiders but allowed them to draw from countless experiences when needed. Among these are the Hekatonystika, an order shrouded in extreme secrecy but uniquely experienced in a special art of warfare. A Paladin may on occasion be assigned from the orders of the Inner Circle to take the lead in a situation where the order's experience would prove absolutely necessary.

The Paladin of the Hekatonystika is a unique consul introduced in the Liber Astartes of the HH tabletop reboot, given a Terranic Greatsword and can select one of the choices for the Orders of the Hekatonystika given to the Inner Circle Knights Cenobium. With the bump to Leadership and WS as well as Stubborn, one could see the Paladin as an improved Consul Champion, though not honour-bound to accept any challenges.

Phoenix Champion

The Phoenix Guard are the most elite terminators of the III Legion, masters of combat and icons of Fulgrim's pride. The Phoenix Champion is the most elite of these guardians, acting as the shining exemplar of a legion that prides itself on outright perfection.

The Phoenix Champion is a unique consul introduced with the Liber Hereticus of the HH tabletop reboot. These consuls gain the same special rules as the Phoenix Guard as well as the masterful Phoenix weapons given to them.