The Horus Heresy: Age of Darkness — 3.0

The Horus Heresy is a tabletop wargame set in the Warhammer 40,000 universe, specifically during the historical event known as the Horus Heresy. In this game, players command armies of Space Marines and other forces, battling for control of objectives and ultimately shaping the fate of the galaxy. The game focuses on recreating the epic conflict between the loyalist Imperium and the traitor forces led by Horus, the Emperor's favored son, as they clash in a galaxy-spanning civil war.
The last update of rules content was done on 08/23/2025. I'm working on getting more rules added as soon as I can. The current rules content are taken from the Core Rule Book and the Liber Astartes. I will add the other Libers once I have finished with these.

Augury scanners allow attacks to ignore Shrouded damage mitigation tests.

When a shooting attack made by a unit that includes any models with an augury scanner inflicts any hits ( excluding hits from attacks made as snap shots ) Shrouded damage mitigation rolls cannot be made against those hits.
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Boarding shields grant a 5+ invulnerable save, the Shield Trait, and the Heavy sub-type.

A model with a boarding shield gains a 5+ invulnerable save.  In addition, it gains the shield trait and the heavy sub-type.
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A cognis-signum allows more accurate attacks to be made with Barrage Weapons.

Instead of making a shooting attack with a model with a cognis-signum, the controlling player may instead make an Intelligence check.  If the check is passed, the controlling player may select a single enemy unit within line of sight of the model with the cognis-signum.  The next time the selected enemy unit is targeted by a shooting attack that includes any weapons with the Barrage(X) special rule during the current shooting phase, the controlling player may make hit tests for the attacks that have the Barrage(X) special rule as normal, ignoring the limitations of the Barrage(X) special rule if the unit making the shooting attack is without line of sight to the target unit.  If the check is not passed, the cognis-signum has no effect.
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A combat shield grants a 5+ invulnerable save against melee attacks and a bonus to focus rolls.

A model with a combat shield has a 5+ invulnerable save against attacks made with Melee Weapons.  In addition a model with a combat shield gains a +1 modifier to focus rolls made for it.
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A command vox relay grans a bonus to reserves tests and can be used to grant other benefits.

While a model with a command vox relay is on the battlefield, before making a reserves test for a unit in reserves, the controlling player can select for that model to activate that command vox relay.  If they do they can modify the result of that reserves test by a +1.  Only one command vox relay can be activated for each reserves test.

In addition, in the effects sub-phase of the start phase, the controlling player of a model with a command vox relay can make an intelligence check for that model ( if that model has the vehicle type, it is treated as having an intelligence characteristic of 8 ).  If that check is successful, the controlling player can select a friendly unit which includes only models with the same faction trait as the model with the command vox relay and select one of the following effects:
  • Until the end of this turn, models in that unit gain the Line(1) special rule ( and lose the Vanguard(X) special rule if they had it ).
  • Until the end of this turn, models in that unit gain the Vanguard(1) special rule ( and lose the Line(X) special rule if they had it ).
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A company standard adds a bonus to combat resolution.

When resolving a combat in the resolution sub-phase of the assault phase, score 1 combat resolution point for each unit in that combat that has any models that have a company standard.  In addition, a model with a company standard counts as an additional 5 models for the purposes of outside support in a challenge.
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Cortex controllers allow Automata to make reactions.

A unit that includes any models with the Automata type can ignore the restriction on making reactions imposed by the Automata type while it includes one or more models with a cortex controller.
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Cyber-familiars grant a bonus to intelligence checks.

The controller player of a model with a cyber-familiar can modify the results of intelligence checks made for that model by -2.
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Dozer blades allow models to ignore the movement penalties of difficult terrain.

If the controlling player chooses for a model with a dozer blade to enter any area of difficult terrain, the unit does not apply a modifier to its movement during that phase.
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Frag grenades can be used to make attacks during the volley step.

When making volley attacks during step 4 of the charge procedure with a unit that includes at least one model with frag grenades, the controlling player may choose to make a single attack with a frag grenade instead of making a normal shooting attack using the following profile:

R:FP:RS:AP:D:Special Rules: Blast(3")  Traits: Assault
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Legion standards grant bonuses to combat resolution.

When resolving a combat in the resolution sub-phase of the assault phase, score 2 combat resolution points for each unit in that combat that has any models that have a legion standard.  In addition, a model with a legion standard counts as an additional 6 models for the purposes of outside support in a challenge.
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A narthecium allows recovery tests to be made in the morale sub-phase.

If a unit that includes any models with a narthecium is not locked in combat, before the controlling player makes a characteristic check for that unit during the morale sub-phase, they can make a recovery test for that unit.  If that recovery test is successful, that player can subtract -2 from the result of the characteristic check.  Only one recovery test can be made for each unit in this way during each morale sub-phase.
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Nuncio-vox allow units to remove statuses in the start phase.

If a unit includes one or more models with a nuncio-vox, and there are one ore more friendly models on the battlefield with the command sub-type, then the controlling player may activate the nuncio-vox during the start phase of their turn as the active player.  When activated, the controlling player may make a check to remove a single tactical status from all models in the unit that includes the nuncio-vox.  This check is made using the characteristics of any one friendly model on the battlefield with the command sub-type, chosen by the controlling player ( using Cool, unless attempting to remove Routed, in which case Leadership is used ).  A nuncio-vox can only be activated once per turn and each friendly model on the battlefield with the command sub-type may only be used once per start phase as part of this special rule.
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Searchlights allow attacks to ignore shrouded damage mitigation rolls.

The target number of any shrouded damage mitigation tests is increased by +1 ( to a maximum of 6+ ) when making tests as a consequence of wounds, penetrating hits, or glancing hits inflicted by shooting attacks made by a model that has searchlights and has line of sight to the target unit.  Additionally, a model with searchlights may not make shrouded damage mitigation tests to negate wounds, penetrating hits, or glancing hits.
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A model with a servo-arm repairs additional wounds or hull points when using the Battlesmith(X) special rule.

Each time the controlling player of a model with a servo-arm selects the repair option when activating the Battlesmith(X) special rule for that model, increase the number of hull points or wounds gained by the target model by +1.
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Thermal diffraction fields reduce the damage of wounds inflicted by weapons with specific traits.

A model with a thermal diffraction field reduces the strength of all hits inflicted on it by weapons with the Las, Plasma, Melta, and Flame trait by -1.  In addition, when any misfire groups are generated by a model with a thermal diffraction field as a result of the Overload(X) special rule, any instance of the Breaching(X) special rule on those hits will only take effect on a wound test of 6+, regardless of the value of X.
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A vexilla adds a bonus to combat resolution scores.

When resolving a combat in the resolution sub-phase of the assault phase, score 1 combat resolution point for each unit in that combat that has any models that have a vexilla.
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