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  • Death in Metal, Part 1: Terror in the Trenches – Trench Construct Encounter for D&D 5e
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Mechanical zombie encounter for parties of 2nd-level or higher, with stat blocks for use in D&D 5e.

The warfront is pushed to and fro as either side takes and then loses the advantage. It is not uncommon for dead and injured soldiers to be lost in the fray of shifting conflict, left behind in the myriad trenches and bunkers. These fallen would be regarded as regrettable losses were it not for the efforts of their compatriots and courageous medics carrying them back to safety. Yet, recently, there have not been any bodies to return.

Increasing numbers of injured have vanished, swept away by unknown hands before any rescuers can arrive. In some cases, only moments pass between the cries of the wounded and the arrival of help, yet no trace of the victim is found. Until they return, that is. Soldiers on the frontlines have reported narrowly escaping from monsters bearing the faces of their fallen allies, with bodies of twisted flesh and metal. Most have not been so lucky as to survive and those that fall appear to return amongst the enemies the following day. With their numbers thinning as the enemies’ grow, the soldiers have had no option but to gradually retreat, leaving many of the infirmed behind and angering their superiors as they lose ground.

One such soldier is Baras Felton, whose post came under attack by the elusive monsters. Baras’s squad was overwhelmed and devastated. He was one of two survivors and the only one to escape, while the other, Ordan Fyura, hid from the attackers. Ordan was injured in the attack and is unlikely to last much longer without rescue. Knowing this, Baras pleads with anyone he can for Ordan to be found and returned. His superiors have denied his request due to the risk and no other soldiers would dare defy the orders, but a group of adventurers with no formal affiliation may just be able to brave the trenches and save Ordan from joining the ranks of the Arma Mortis.

Accepting the assignment. Should the party agree to look for Ordan, Baras provides directions to his hiding place and a description of what to look for. He also quietly gives them advice on how to sneak past the closest patrols and enter the trenches, in case the characters are unable to secure permission to leave.

The basis for the encounter is intentionally vague in regards to some details, as it can vary greatly depending on its context within your game’s world. The party may be allied with the army on their side of the trenches or they may be completely unaffiliated, and the same goes for the scientist behind the creation of the Arma Mortis, who will be covered in part 2 of the encounter. If the opposing army is seen as the characters’ enemies, you may wish to make the Arma Mortis an extension of that army, with their creator being contracted to help win the battle or war. If not, the scientist may be a third party, opportunistically using the battlefield for his own means. Or perhaps he is formally affiliated with their army but shows no loyalty to them and has commanded the Arma Mortis to attack both sides? All of these explanations are perfectly viable and hinge upon the events of your particular story and world. They can also open the door to interesting additions, such as the latter examples allowing for the party to encounter a squad of opposing soldiers in the trenches who have also come under attack and with whom the characters might be able to form an uneasy alliance.

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The Trenches

The trench carves through desolate, sodden earth, branching off in interconnecting lines. Hastily erected wooden supports and sandbags hold back the worst of the mud, yet it has still found its way onto every surface and the ground is still wet from bouts of rain, dulling the otherwise pervasive smell of smoke and metal. Though there is chattering and the splashing of boots behind you, the distance ahead is veiled in cold, anxious silence.

A sprawling network of trenches cuts into the area dividing the two armies, whose respective frontlines have advanced and retreated as the tides of the battle shift. This has left much of the trenches empty yet dangerous to traverse for fear of stumbling upon enemy soldiers and even more so for the recent advent of monsters stalking the pathways. The trenches themselves only worsen this, as their construction has shifted and developed according to each side’s changing needs, yet never with comfort in mind, resulting in what is now a confusing, guideless array of silent paths, bunkers, and makeshift rooms.

Tunnels and pathways. The trenches have been dug uniformly to be 15 feet wide and 7 feet deep, with steeply sloped walls. They feature no sources of light, though some unlit torches and lanterns may still be found where they have been left behind.

If you wish to add extra danger, include the possibility of being attacked by the opposing side if a character stands or moves higher than the sides of the trenches and is seen by enemy soldiers. Including the threat of enemy fire is an effective way of adding suspense and keeping the party confined to the trenches themselves, while stealth and cover rules should mitigate how frequent and damaging these attacks may be, helping the Arma Mortis remain the encounter’s dominant threat. The part could still escape from an ambush by climbing out but doing so would carry its own risks.

Map & Asset Downloads

The Arma Mortis were inspired by our own ‘WW1 Trench Map Assets’, which make for the perfect environment for the encounter. But they are not the only place that the Arma Mortis could appear, and we have plenty of assets for other encounters in which you might use them…

Ordan Fyura

(CG male halfling scout)

The halfling man wears an exhausted, pallid expression. His skin and soldier’s uniform are slick with a mixture of dirt and sweat, obscuring him against his surroundings but doing nothing to hide the expansive bloodstain coating his right leg.

Ordan is another soldier who was stationed in the foremost trenches alongside Baras. He is a quietly confident individual and a natural leader, making him well-liked amongst his comrades. Though he tries to maintain this demeanor, the loss of said companions in addition to his own injuries have made it easier to see through Ordan’s fortitude.

When they came under attack, Ordan did everything he could to help other soldiers escape, though only Baras was ultimately successful and Ordan himself suffered an injury to his leg. Unable to move quickly, he ordered Baras to flee. Baras helped Ordan hide under a sleeping cot in a small bunker, collapsing other furniture to hide him, before he escaped. Ordan has remained in the hiding place, silently hoping that the attackers do not return.

Ordan remains hidden unless he hears the characters calling out his or Baras’s name, at which point he tries to attract their attention. He stays quiet and attempts to hush them in fear of the monsters detecting them but thanks the party for their arrival and explains his injuries. Ordan can easily lead the group back through the trenches but is unable to fight effectively in his current state. He speaks affectionately of Baras if the latter is mentioned, remarking that he never doubted that Baras would send help and only worried that he’d do something foolishly brave in the process.

Injured leg. Ordan’s right leg was badly injured during the attack. He has only 10 hit points when the party finds him, and has three levels of exhaustion until he is healed for at least 5 hit points.

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The Arma Mortis

Though the place where injured soldiers are taken remains unknown, the fates of its victims do not. They reemerge as members of the Arma Mortis, a horde of twisted amalgamations of machine and man that, fueled by an unknown substance and charged with electricity. These monsters run rampant through the trenches yet maintain robotic coordination and efficiency. They stalk the remaining soldiers in coordinated packs that isolate, incapacitate, and then disappear back into the deeper trenches with their prey, who return as Arma Mortis themselves shortly after.

Mortis Drone

CR 1/8

The greyed form of a person lumbers forward, its arms missing and what remains of its body enhanced with metallic fixtures. Braces hold to its legs, joints whirring. Pipes wind through its torso and neck, pumping green liquid that leaks from loose connections. And its mouth chitters open, its lower jaw removed and replaced with sharpened robotic mandibles.

The greyed form of a person lumbers forward, its head missing and what remains of its body enhanced with metallic fixtures. Braces hold to its limbs, joints whirring. Pipes wind through its torso, pumping green liquid that leaks from loose connections. And its hands flex and spasm with sharpened metal claws.

The greyed form of a person crawls forward, its legs missing from the waist, a metal spine dragging behind like a tail, and what remains of its body enhanced with metallic fixtures. Braces hold to its arms, joints whirring and fingers affixed with sharp metal claws. Pipes wind through its torso, pumping green liquid that leaks from loose connections. And its mouth chitters open, its lower jaw removed and replaced with sharpened robotic mandibles.

The mortis drones are the most basic of their kind. They are the leftovers of the most grievously wounded or those whose limbs were deemed to be more useful if given to another subject. The remaining bodies are granted the minimum enhancements needed for animation and then sent back into the trenches to hunt at the command of their more advanced kin.

Mortis Hound

CR 1/4

A warhound’s body is enhanced with crude metallic mechanisms, sections having been replaced in their entirety with robotic facsimiles. Its torso has been hollowed of organs, leaving an exposed metal ribcage, and its neck has been rebuilt with an embedded collar of concave chamber-like devices.

The first of the horde to locate new victims are its scouts, the mortis hounds. The hounds use their speed, maneuverability, and tracking senses to rush through the trenches in search of targets before howling, the devices on their necks amplifying the sound into a disorienting scream that alerts anything nearby. They then harry their prey with attacks to slow and separate them while the rest of the Arma Mortis descend on the location.

Mortis Hunter

CR 1/2

A glint of light draws your eyes upwards to a humanoid shape. A helmet and leather mask cover the individual’s face. The lenses of its eyes glow green and pipes funnel into its mouth and wind through its grey flesh between plates of rustic metal armor. Gyros reinforce its limbs, attaching to wings of metal and canvas. These connect like a bat’s to the person’s torso and arms, which themselves end in mechanized claws with middle fingers that extend into long, scything blades.

Perhaps the most terrifying of the Arma Mortis are the mortis hunters. These hunters, crafted from the most able-bodied of their victims, lead the charge against any prey that their hounds locate. Their wings and claws allow them to easily traverse varied terrain and strike from any angle, debilitating or outright killing targets already under attack by the mortis hounds and drones. Those that escape can never do so for long, as the hunters gain their quarry’s scent from the blood on their claws and use it to track them no matter where they run. 

Mortis Harvester

CR 1

The inside of the figure’s hooded leather coat is illuminated in dull green by a liquid swimming in tanks set in the creature’s skin. The light exposes its sunken flesh and the metal and piping that is grafted to it, though its face is covered in a mask of metal and leather, which the pipes flow into. It walks with a hunch, movements clicking mechanically, and brandishes a pair of sickles. 

When their targets have been chosen and the Arma Mortis have commenced their attack, the harvest begins. Mortis harvesters arrive shortly after the hounds and hunters and are tasked with securing victims, alive or dead, to be transported back to the laboratory where the Arma Mortis are produced. They do so with the use of limited magic that their creator inscribed into their mind. This allows them to strike from the shadows with their dual sickles, activating the hunters’ unique augmentations to siphon the life from their victims and pass it to their allies, protecting and overcharging them.

Mortis Behemoth

CR 6

An armor-plated humanoid of monstrous proportions forces itself through the trenches. Its enlarged, elongated arms support spiked tower shields, their weight carving into the muck as it advances. Armor of similarly thick metal plates covers much of its bloated musculature, supporting tanks of green fluid and pipes set into the behemoth’s flesh. These enhancements flow to and support the weight of a monstrous weapon mounted on its shoulders in place of its head; two rune-inscribed prongs that extend from a shared engine, crackling with energy of the same putrid color as the liquid pumping into it.

Monstrous, hulking forms lumber through the trenches, their size almost blocking the pathways. No soldiers can adequately describe these creatures as none have survived witnessing one, though they can shakily recount a name derived from the sounds of the monster and the destruction it wreaks: the mortis behemoth.

Should one encounter a behemoth, they will find themself facing down the most physically powerful of the Arma Mortis. Behemoths are designed to lead the charge with their nigh impenetrable defenses and devastate entire groups of enemies with their mounted mortis cannon. They are mercifully few in number and wander independently rather than with others, slowed down by the weight of their augmentations. Yet they are no less threatening, as a single behemoth can decimate entire groups of soldiers in a single attack, the resulting blast and screams often alerting nearby hounds.

Worried that a behemoth’s Mortis Cannon attack might TPK your low-level party? Be sure to give them ample warning of its approach and the charge of its cannon, or have the party witness a behemoth firing on another group of soldiers so that they can see the damage it does. If one appears in the midst of combat, you may wish to roll to see if its cannon recharges, or simply describe it readying to fire, at the beginning of the round rather than on the behemoth’s turn. This gives faster characters time to react without compromising the threat of the behemoths.

Balancing the Arma Mortis

The Arma Mortis are in control of the trenches where Ordan is hiding and it is up to the party to get in, find him, and get out safely. This means that their success is likely to dictate how many creatures they attract and are forced to fight. Fortunately, the various Mortis units’ roles provide an effective starting point for how you can influence the encounter’s balance.

Should the characters draw the attention of a mortis hound or drone, the monsters that follow are likely to arrive in staggered waves as they approach from various distances and at different speeds. This allows you to control the pace and difficulty of the encounter as it plays out. You are able to slow or even halt the addition of extra units if the characters are being overwhelmed too quickly. The area of the trenches should ideally be large enough that this form of engagement may occur several times with moments of quiet in between, though this may depend on the party’s success. And while you may wish to err on the side of caution, it is also fitting for the encounter to be difficult, and potentially deadly, due to its context and to instill a feeling of danger should the party make repeated mistakes.

The only outlier to the Arma Mortis’s tactics is the mortis behemoths. The behemoths do not rush to engage in ambushes and are instead designed as dangerous, wandering obstacles that the characters should try to avoid. This means that their Challenge Rating can be excluded from many of the individual fights, though it should still be kept in mind in case the characters enter combat close enough to a behemoth to attract it. The number of behemoths must likewise be considered to not overcrowd the trenches. Ultimately, if a behemoth is too likely to TPK your group, you can always simply exclude them from the trenches that the party is traversing.

Finally, you also have the option of bolstering the party’s numbers by having them encounter other groups of soldiers within the trenches. These soldiers can be simple scouts, thugs, and even acolytes, and can help for a single bout of combat or accompany the characters through the encounter. Adding to their side allows you to raise the CR of the enemy groups for more varied combat encounters. Just be wary of outnumbering the characters with additional soldiers as it can quickly steal the limelight from the party. One way to avoid this is by giving the players command of these other fighters in combat, having them either issue orders or control them completely, thereby keeping them in control of their entire side.

Here are some examples of creatures that you may use to achieve different CR values for individual ambushes in the trenches:

CR 1: 1 mortis hunter, 1 mortis hound, 2 mortis drones

CR 2 1/2: 1 mortis harvester, 2 mortis hunters, 2 mortis hounds

CR 7: 1 mortis behemoth, 1 mortis hunter, 1 mortis hound, 2 mortis drones

CR 9: 1 mortis behemoth, 1 mortis harvester, 2 mortis hunters, 2 mortis hounds, 4 mortis drones

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About the author

Troy McConnell

Part-time DM and author of 2-Minute Tabletop's encounters, map lore, and characters. Basically, I write about all the campaign ideas that I don't have time to run. All with the assistance of my feline familiar, Wink.

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