Ruleshammer: Guide to Terrain in 9th

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With the new edition nearly upon us, we had Rob “Vre’kais” Chilton sit down with the new rulebook in the Indomitus boxed set and write his thoughts (in great detail) on the new rules – what’s changed, what needs clarification, and what you need to know. At the halfway point, today one of the biggest articles yet as Rob delves into the Terrain rules.

Terrain has gotten a lot more nuanced in 9th edition, most of it for the better though it’s not without it’s quirks. As I explored how some of the new rules are written and how some of them are summarised there’s certainly a few traits that might need inclusion in the Day 1 FAQ.

Terrain Categories

In 9th every piece of terrain must be assigned one of four categories.


The Hills Terrain Category defines them as not being terrain features. They are considered part of the surface of the board. They block LoS in the usual way if your models are behind them but they gain no terrain traits and models on top of them do not typically receive any additional benefits. Abilities such as the Raven Guard chapter tactic that requires the unit to be on a terrain piece would not be triggered by being on a hill, as they are not considered to be terrain pieces even if they are free standing rather than sculpted into the board.


Obstacles are the smaller solid pieces of terrain like Statues, Barricades, Ruined Walls that you models have to move over or around. Models receive benefits of cover (if there are any for that terrain piece) whilst within 3” of the Obstacle terrain and if they have the INFANTRY, BEAST or SWARM keywords.

What’s interesting about this though is that Obstacles on their own do not define a “benefit of cover”, so if the obstacle lacks a cover Terrain Trait then it’s entirely possible whilst near them to “have the benefit of cover” and that benefit be nothing at all. Also obstacles only provide cover to Infantry, Swarm and Beasts whilst within 3” of the obstacle,

…unless, when you resolve an attack that target’s a models unit, you can draw straight lines, 1mm in thickness, to every part of a models base from a single point on the attacking model’s base (or hull) without any of those lines passing over or through any part of the terrain feature. [Obstacles – Book Pg260]

The Dense Cover Terrain trait works in a very specific way with this terrain category, which is covered later on in this article.

Area Terrain

What is likely the most common type of terrain, area terrain is any terrain that covers an area. Sometimes this will be denoted by a base but it might not be or the base might be a beautifully sculpted terrain piece in it’s own right. It’s important to agree on the boundary before the game starts.

Here’s a very important part of Area Terrain, Infantry, Beast and Swarm units receive the benefits of cover from Area Terrain whilst they are within them. It’s taken a lot of back and forth at Goonhammer HQ but the “best” interpretation we have of this, that causes most of 40k’s terrain traits to work as expected is that these unit types always gain the benefit of whatever cover traits the terrain has whilst they are within, regardless of the usual check for them. Other unit types however do not gain the benefit of cover whilst they are within them. This might seem obvious but there are types of cover in 9th you can benefit from whilst not being within area terrain, see Dense Cover below.

Disclaimer: This isn’t explicitly said in the rules though, it just lists that Infantry, Beast and Swarm gain the benefit. I’m going to be keeping my eye on the FAQ if my interpretation turns out to be inaccurate though.

Similar to obstacles, whilst Area Terrain features give units within or partially on them the benefit of cover they  do not actually define an actual benefit.


Buildings are still typically units with the Fortification Battlefield role and the BUILDING Keyword. [Book pg261]

Like Hills Buildings are not considered to be Terrain Pieces, they are instead considered to be units. They follow the usual rules for Line of Sight when models are shooting around them. This is pretty much exactly as it was in 8th but it’s now a more defined part of the rules.

Terrain Traits

Before we look at the Terrain Traits I want to make a quick note about ignoring cover weapons, they are covered by the new rule books Appendix in the new “Rare Rules” section (not that they’re especially rare). We’re going to cover all of the Rules in that section next week, but cover is in there and it’s handled well in my opinion.

Moving on though, the new terrain traits. We’ll start with the two that are in my opinion going to be some of the most significant changes to 9th.

Dense Cover – Affects Hit Rolls

Most of Dense Cover was included in a preview, along with its bullet points.


Source: Warhammer Community


There is an extra bit missing though that helps make the bullet points make sense.

Models do not suffer this penalty to their hit rolls when making an attack with a ranged weapon that targets an AIRCRAFT unit, or a unit that includes any models with a Wounds (W) characteristic of 18 or more, even if this terrain feature is between it and the firing model (note that the reverse is not true). [Book pg262]

So what does Dense cover do? Well the scenario it’s mostly design to create is like this.



However it has that line about drawing lines an entire models base (or hull) so it also conveys cover in situations like this.

Amendment: The examples below are based on a pretty pedantic reading of the words “over or through”. Essentially that “over or through” means that the attack would cross one boundary of the area terrain (or obstacle) then cross another so that it has gone all the way “over or through” the terrain before hitting the target. This supports the Devilfish in Fig 2 below gaining the -1 to hit benefit when the Necrons shoot. However if the Devilfish is within the terrain then the shots aren’t going “over or through” but instead “into”, I did say it was pedantic and it’s not 100%. This would prevent any models from claiming the Dense Cover benefit whilst within Area terrain or near Obstacles. However both of those terrain categories say that models with the INFANTRY, BEAST or SWARM keywords can claim the benefits of cover that the terrain has whilst they are within them, giving those models the cover benefit back unless the firer can see an entire model’s base (you have to slow roll this though as Dense cover affects hit rolls and is resolved when resolving attacks). We will be monitoring any updates or FAQs to these rules and update these diagrams and explanations as soon as that occurs. I know this isn’t a 100% solid interpretation, but is a fair one and the others had similar issues. Interpretations where vehicles could never benefit from Dense Cover and interpretations like the Turret diagram below here.

However that’s when the models are not within the terrain, and we’re using Dense Cover’s rule on it’s own to determine if any benefit of cover is gained. When models are within Area Terrain they gain the benefit of cover if they are INFANTRY, SWARM or BEAST. Whilst I acknowledge this is quite a strict interpretation of the Area Terrain rules I think the most supported interpretation is that models without those keywords don’t gain the benefit whilst within Area Terrain.


Disclaimer: As previously stated I can’t claim that this is the only interpretation that we’ve had for these rules, but it’s one that is Rules as Written (though so are others) and one that doesn’t lead to the odder things like if a tank has it’s turret over the boundary of a piece of area terrain, would it gain the dense cover bonus? To draw lines to every part of it’s hull some of them would pass over or through the terrain piece.

Some of The Chirurgeon’s best work.

My reading of the rules is that as the turret is “within” that Tank would not get cover because they are not INFANTRY, BEAST or SWARM. For a tank to gain dense cover’s benefit from this terrain they would need to be on the other side of it and not within it.

Obscuring – Affects Line Of Sight

Credit: Warhammer Community

First things first, when you get your rule books and find these rules Obscuring Terrain has an issue. The Rule and it’s summary Bullet Points contradict one another.

In cases like this my approach is to go by Rules As Written not Bullets as Written, as they are meant to summarise a rule not define it. So with that in mind what does obscuring do? Before we get to any diagrams there’s a fundamental bit of wording to make a distinction about.

Models that are on within this Terrain feature can be seen and targeted normally. [Book pg263]

This means you use the normal Line of Sight rules, the models you target need to be visible through windows or gaps as this is what you do “normally”. “Can be Seen” means it’s possible, not that you are automatically visible to the entire board. The reverse is also true, models within the terrain can see and target out normally. Frustratingly this isn’t written specifically, but the second part of Obscuring calls out that the reverse of that part is “not true”, implying that is is true here.

AIRCRAFT models, and models with a Wound Characteristic (W) of 18 or more, are visible and can be targeted even if this terrain feature is in-between it and the firing model (note that the reverse is not true). [Book pg263]

Here “are visible” does mean they pass the visibility test of target selection regardless of what the firing models can actually see. This language is very specifically chosen but understandably confusing. It also notes that the reverse is not true, so AIRCRAFT and models with 18 or more wounds don’t treat targets that can shoot them as automatically “visible” in return. Corrode: I am fully expecting that this gets erratad so that normal line of sight rules apply as seems intended, rather than obscuring allowing you to wallhack to shoot at Knights you can’t see at all.


So let’s look at some practical examples of how obscuring changes the battlefield.

Also note that the 5” criteria for Obscuring Terrain only limits whether or not the terrain piece blocks line of sight to other “small” things. The part of the rule concerning Aircraft and models with 18 or more wounds does not require the terrain piece to be more than 5” tall to apply, obscuring terrain just never blocks Line of Sight to them. It would be a bit odd if the shorter terrain pieces suddenly swapped back to using normal Line of Sight for them.

Note: Based on some very good feedback, it’s unlikely that the diagram above will remain accurate. Mostly because whilst it might seem relatively sensible that a model can peak around one solid ruin to see a Knight, the current “are visible” wording would allow them to do so around lots of ruins. This seems a bit much.

Defensible – Affects Overwatch Or Combat Hit Rolls


Defensible terrain allows INFANTRY units either on or in Area Terrain, or INFANTRY within 3” of an Obstacle (that at least partially hides every model in the unit) to either Hold Steady or can be Set to Defend. They can not do either whilst within Engagement Range of enemy models though.



Defence Line – Affects Charge and Fight Range

Similar to the barricades rule from 8th, but tidied up a bit. Units within 1” of this terrain feature can be charged so long as the charging unit ends their move touching the terrain piece and within 2” of the target unit, and units can be selected to fight and models make melee attacks at a range of 2″ rather than 1″ if their target is on the far side of the terrain.

Breachable – Affects Movement

The old move through Ruin Walls rule from 8th but now it’s own thing. INFANTRY, BEAST and SWARM units can move through walls, girders etc without impediment. Having this separate from Ruins is one of my favourite changes in 9th because it allows you to decide with your opponent which Ruins are open and exploitable and which terrain pieces are a little less “Ruined” and that models can’t enter. Not applying this trait to a Ruins with four intact walls and a ceiling removes the entire concept of “enclosed ruins” from the game.



Difficult Ground – Affects Movement

This trait takes the -2” to movement that Forests and Craters had and applies it to units making Normal Moves, Advances, Falling Back or Charge Moves where any of their models move over the terrain. That’s a pretty big change, as it used to only apply to charges, and it’s important to note that the whole unit gets slowed down even if only one model touched the terrain. Heroic Intervention, Pile In or Consolidate moves are safe, however!

Light Cover – Cover Benefit

Makes the benefit of cover for a terrain feature “add 1 to save throws against ranged weapons (this does not affect invulnerable saves).” Essentially this is just the normal cover from 8th edition.

Heavy Cover – Cover Benefit

Makes the benefit of cover for a terrain feature “add 1 to save throws against melee attacks unless the model making the attack made a charge move this turn (this does not affect invulnerable saves)”. Yes you read that right, it’s cover against melee UNLESS model attacking charged this turn, not that units that charged don’t get the benefit. Honesty I don’t quite know what this rule is trying to do. Don’t leave space for charging units to get into cover with you though, or they’ll have +1 to their saves.

Wings: Our theory in the Goonhammer offices, sort of backed up by the bullet points, is that this might have been intended for the charging unit to lose the benefit rather than the charge target. That feels like it would make a lot more sense.

Unstable Position – Affects Movement

Models cannot be set up or end a move on top of this terrain feature (they can move up, over and down this terrain feature, but they cannot end a move on top of it). [Book pg263]

This is an interesting one, on the one hand it could be used on some terrain to prevent someone from balancing a sniper on a spire, or from balancing a Repulsor on a 0.5” wide ledge. The issue that the latter idea has though is that if the ledge you wanted to keep Repulsors off was closer to 1.5” then it’d be very harsh to rule such a space off from any and all models. It’s also not clear from the wording of this rule if it includes placing models on middle floors.


Exposed Position – Cover Disabler

This trait prevents models from gaining any benefit of cover whilst on top of the terrain feature. Cover can still be gained by being “behind” it. Again “on top” is not defined but the suggested types of terrain for this trait are things like storage containers which often have several different heights. I would recommend just agreeing with your opponent to treat each container separately so that they all have an “on top” of their own

Scaleable – Affects Movement

This trait has two distinct parts. The first part allows units to be setup or end moves on top of these terrain pieces.

Only INFANTRY, SWARM and BEAST models, and models that can FLY, to be set up or end a move on top of an Obstacles terrain feature with this trait. Only INFANTRY, BEASTS and SWARM, and models than can FLY, can be set up or end their move on the upper floors of an Area Terrain Feature with this trait (other models can be setup or end a move on the ground floor). [Book pg263]

The second part is actually a terrain rule that is now separated from the Breachable rule we covered earlier. That rules was about vertical barriers such as walls, pillars, or trees. The scaleable trait allows movement through horizontal barriers like floors, ceilings or gantrees.

This is quite significant as it really allows for some terrain feature customisation that 8th never allowed for. Industrial terrain such as this.


Credit: Games Workshop

By giving it the Scaleable trait but not the Breachable trait you allow models to move through the gantrees but not through the solid walls or girders (which they can quite easily move around anyway). This prevents issues such as “can my model go inside this terrain”.

Inspiring – Leadership Booster

The last type of terrain gives a +1 leadership (ld) to any units within 6”. It can also be given a Faction keywords which limit the effect to units that share that faction keyword. This is similar the Imperial Statue rules from 8th but allows for other factions to have their own equivalents.

Wings: Delighted to see that there is finally rules support for elegant, sophisticated elf statues and not just gaudy eagle-heavy monuments to some basically dead guy.

Terrain Conclusions

So in conclusion, there’s a lot of terrain rules now and the combinations of traits really open up some board to have really interesting terrain. Some of the new rules are very confusing, some of them are summarised in way that just add to that confusion. The majority though are great and this article has hopefully provided a framework for using them all to improve everyones games. I do have more to say about what traits are suited to different types of terrain, that’s coming next week. If you have a terrain piece that you think might interest me in this feel free to share it in the comments or with me on Reddit on r/ruleshammmer.

Have any questions or feedback? Got a rules question you want answered? Drop us a note in the comments below, ask a question in our Ruleshammer form, or head over to r/ruleshammer to discuss.


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