Reactions are the biggest change in the new edition of Horus Heresy, adding opportunities for the opposing player “react” to things in the Movement, Shooting and Assault phases. 

A Reaction is an ability which allows a Reactive Player to take an action in their opponent’s turn. Reactions sort of existed in the previous edition, in the form of Overwatch. Reactions have been fully fleshed out, adding some fun and flavorful thematic scenes to your games.

Each player has a Base Reaction Allotment. This is 1 Reaction per phase of your opponent’s turn – so one in the Movement, one in the Shooting, one in the Assault phase.

You can increase the Base Reaction Allotment with some Warlord traits, characters, powers and abilities. This can increase the amount of reactions you can use per phase, up to a maximum of 3.

You cannot do a Reaction if you are Pinned or Falling Back, or if you have already done a Reaction in that phase with that unit. 


Movement Phase

If an enemy unit ends its move in line of sight and within 12”, you can take a Reaction. 

Advance – move up to your Initiative value directly towards an enemy unit which triggered the Reaction. Vehicles can pivot 90 degrees and move 6” forward. 

  • This can be very useful for assault armies, allowing you to get that bit closer to the enemy. I can also see this being very useful late in the game to get closer to, or capture objectives.

Withdraw – The Reacting Unit can move up to its Initiative value directly away from the enemy unit which triggered the Reaction. Vehicles can pivot 90 degrees and move 6” backwards.

    • The opposite of Advance – you’ll see this used for ranged units wanting to avoid an assault or to draw the enemy into well planned traps.

Shooting Phase

If an enemy unit shoots one of your units, after Armour Saves but before Damage Mitigation and casualties, you can choose to take a Reaction. 

Return Fire – You can make a Shooting Attack against the unit which triggered the Reaction. Vehicles can fire Defensive weapons Template Weapons can Wall of Death if the enemy is within 8”. 

    • This reaction will make you think a little bit more about what enemy units to shoot and what of your units you will use to shoot them. No one wants 10 lascannons shooting back at your predator squadron that just clipped the enemy with a plasma cannon.

Evade – All models in the Reacting unit (provided they can move) gain Shrouded (5+), which is a mitigation save taken after armour saves, like feel no pain. 

    • This can be very uceful if you want to keep that elite unit around a little while longer. If your terminators are about to be pummeled by that melta gun support squad, it gives your a greater chance of hanging around.

Assault Phase

If you have a Charge declared against you, you can choose to React. 

Overwatch – You make a shooting attack at full Ballistic Skill, with Templates using Wall of Death. 

    • This is much more powerful than older editions, but is off-set by the fact Reactions are limited and you can Pin units to prevent it. However, running into a twenty man Legionary squad might look a bit dicier if they’re ripping 40 Boltgun shots into you at full BS. 
    • Another thing which might not be obvious, Vehicles can Overwatch now, using defensive weapons.

Hold the Line – Make a Morale check, if successful, it forces a Disordered Charge. If the enemy then fails their Charge, any other Charges which hit the Reacting unit will still count as Disordered. 

    • A key thing to remember is that a Disordered Charge goes beyond simply +1 Attack – things like Furious Charge won’t work, as well as some special weapons and abilities. This is probably going to be used by melee units who are taking a Charge, and so wouldn’t benefit from Overwatching.