Zone Mortalis

Based on the "Blood in the Void" rules for ship-boarding battles in IA9, Zone Mortalis is a ruleset written by Forge World for a way to play close quarters battles in 40k. These rules can be used to make games smaller and faster, but they also make everything deadlier. While you technically can do a game with these rules on a 6x4 table, it's easier if you do them on a 4x4 or smaller table, dropping the points value as you drop the size. Unfortunately, very few 40k players actually used this ruleset. Therefore as of 8th edition 40k, this gamemode has been replaced by Kill Team. However, elements of Zone Mortalis remain an important part of the Horus Heresy game by Forge World.

Building an Army

To play a Zone Mortalis battle, start with how you would start any game of Warhammer: building your army. Unless you're going to be playing one of the missions in the expansion, you need to use the Force Organization chart for a Zone Mortalis Combatant. The only compulsory choices are 1 HQ and 1 Troops, with an optional 1 HQ, 2 Troops, 2 Elites, 2 Fast Attack, and 1 Heavy Support.

There's also the option for Zone Mortalis Mission charts for the Attacker and the Defender with a slight tweak. The Defender gains a Troops and a Heavy Support choice but loses an Fast Attack slot, and the Attacker trades a Heavy Support slot for an Elites one, which is compulsory instead of the Troops. Attacker and Defender can be decided before the game, rolled on, etc.

There's also a number of restrictions:

• No dedicated transports: No driving METAL BAWKSES trough the ZM corridors.
• No unit can have a starting size more than 15 models before being joined by Independent Characters: Note that some ZM specialist units, such as the Solar Auxilia lasrifle section, split into 10 man squads to go around their starting size of 20.
• No vehicles: (except for walkers and models less than 4" wide).
• No flyers: (duh)
• No models with a base bigger than 60mm: Your Leviathan Dreadnought is too CHONK for this mission.

You get a Warlord as the norm, but only in games with 500+ points.

Building the Map

Instead of rolling for terrain like normal, create the inside of a building. Add in walls, intersections, doors, whatever you want! Use your D&D Tilesets! Use your copy of Space Hulk or Assassinorum Execution Force! Use a dry-erase board! Use whatever you want! Or make a regular tabletop map and designate some parts as following the Zone Mortalis rules.

Forge World used to sell an absurdly expensive set of Zone Mortalis tiles, and now there is also the modular set from Necromunda if you're willing to pay for more thematic terrain.

Special Rules

This being Zone Mortalis, a bunch of rules change the value of cover, modify movement, and make weapons scarier. In general, reduce all cover saves from battlefield terrain by 1 to a minimum of 6+ (so sandbags are 6+, ruins are 5+, and bunkers are 4+. However, going to ground in bunkers gives a +2 instead of +1, so there's that). Different models find it harder to move around, now.

• Bikes, Jetbikes, Artillery, Cavalry, and Walkers treat all difficult terrain as dangerous terrain. If they turboboost, they take a dangerous terrain test regardless of how far they go. This ignores whatever their dataslate says about ignoring cover in the way (like the Move Through Cover USR).
• All Jump Infantry and FMCs who move more than 6" have to take a Dangerous Terrain test or hurt themselves flying into the roof.
• All other vehicles (including Skimmers) treat the map as both difficult and dangerous terrain.
• Wrecked vehicles are now difficult and dangerous terrain, not just battlefield terrain.
• Infantry, MCs, and Beasts treat the map as normal (open ground is open ground, difficult terrain is only difficult, etc.)

Also, there are rules for doors now. They come in three varieties:

• Locked doors can only be opened by being destroyed or being unlocked as part of the mission. If the door's destroyed, remove it from play.
• Accessible doors can be opened or closed by the first unit who touches it in a turn, once per turn.
• Controlled doors are accessible by one player, but locked to the other.
• All doors count as AV 13 with 1 HP, so any glancing or penetrating hit will open them up.

All objective markers are impassible terrain which don't block LoS. Capturing an objective requires base contact. Reserves, Scouts, and Infiltrators are unchanged, but they can only enter through the designated entry/exit points. Deep Strikers can only show up if they teleport in (Terminators are okay, Drop Pods are not). Anyone who scatters into a wall or bulkhead gets a Deep Strike mishap and rolls it at a -1 (yay telegibbing!)

Now for the combat:

All blast markers and template weapons get the Shred special rule. Weapons which already had that special rule get +1 S. Weapons which scatter into the wall detonate on contact with the wall. The blast which goes over the wall is absorbed by the wall and lost (so you can't scatter into the enemy Dreadnaut hiding around the corner). Winners of Assaults can reroll their Sweeping Advance if they want. Losers must first fall back directly away from the enemy before they can start falling back to the nearest unblocked exit. If a unit is trapped by an enemy unit and can't go around, they are destroyed. Units which are falling back and pass within 1" of another of their player's units force the other unit to make a Morale test (unless they're Fearless). In other words, grab what spacing you can or watch your entire army run away because of that one squad of cowards. Because of how close quarters the map is, units being assaulted have access to Reaction Fire, which lets a unit being assaulted fire their overwatch at full BS instead of Snap Shots. Note that only Pistol, Assault, Rapid Fire, and Heavy (with relentless) weapons can be shot in this manner. Everyone else can still make standard Overwatch attacks if they want. A unit can only ever make one reaction fire, and it has to be against the first unit they're assaulted by. The unit has to pass an Initiative test first, but that's still a 50% chance on GEQs. However, models with Counter Attack don't get the +1 Attack if they choose to Reaction Fire.

Optional Special Rules

Attrition: When the game ends with a draw, whoever lost less units wins. Might make it interesting if you play with someone who you draw with often.

Enemy Unknown: For when you want to play Stratego-hammer! After you make your army list, number the units on it. Then pull out counters with corresponding numbers on them and place them number-side down. Deploy using the counters instead of the models and play as normal. When two unit-counters are in line-of-sight of eachother, each player flips the counter and replaces it with the corresponding unit. Whenever a unit leaves line of sight, replace it with the counter again.

Cold Void and Poisoned Air: Are your weapons not scary enough? Here's how you fix it!

• All weapons and attacks with S4 or more get Rending (except against targets with Hardened Armor, Void Hardened Armor, vehicles, and 2+ armor). In mixed units, apply the rending hits to the squishier targets first.
• Everything which already had the Rending rule now rend on a 5 or 6 (except against the above exceptions).
• Blasts are now also Pinning.

Catastrophic Damage: Every turn after the first, roll 2d6 and check this table, adding +1 if someone fired an Ordnance weapon on the preceding turn.

• 2-5: No effect, structure stable.
• 6-7: Players roll-off, and the winner places a Large Blast and rolls for scatter. All models underneath takes a S5 AP4 hit. Vehicles are hit rear armor. A portion of the roof collapses.
• 8-9: For this turn, all models are at -1 BS and I (to a minimum of 1). Dust kicks off all across the site.
• 10: All clear terrain counts as difficult terrain. The floor receives bad damage.
• 11: Same as 6-7, but D3 Blasts which are also Pinning. The roof partially collapses.
• 12+: Every model on the board takes a S test. Those who fail or don't have a S value are buried under tons of rubble (removed from play). Independent characters can reroll this test. If a 12+ is rolled again, it has no effect. The building/cave/voidship area completely caves in, burying any unfortunates present alive if not straight up crushing them. Obviously, no more building is left to cave in, though some portions may remain standing to justify further rolls of 6-7 or 11.

See Also

The actual PDF

Rules for Horus Heresy

8th Edition fan rules by Goonhammer

Ways to Play Warhammer 40,000
Apocalypse - Cities of Death - Combat Patrol - Eternal War Kill Team - Maelstrom of War - Planetstrike - Zone Mortalis