🎲 The Setting
Warhammer 40,000 for D&D Players
A One-Page Primer — Read This Before Game Day
You already know how to play 5e. This sheet is the other half: the world your character lives and dies in. Read it once. You don't need to memorize anything — you just need the vibe. The rules are exactly the 5e you know; only the paint is different.
The Pitch
It is the 41st millennium, and there is only war. Humanity rules a million worlds under a god-emperor who has been dying — and worshipped — on a golden life-support throne for ten thousand years. His empire is vast, ancient, fanatically religious, and rotting: it can barely keep its own machines running, it burns whole planets to hold the line one more day, and it is besieged on every side by demons, aliens, and traitors. It is, at best, "technically the good guys" — only because everything else is worse. This is grimdark: the genre that named itself. There are no clean wins here. There is duty, faith, and the candle you hold against an endless night. In the grim darkness of the far future, there is only war.
The Setting — The 41st Millennium
- When/where. Roughly 38,000 years from now, across the whole galaxy. Distances are crushing: a message can take years to cross the void, and a single soldier means nothing — worlds are spent like ammunition.
- The Imperium of Man. Humanity's empire: ~a million worlds, a crumbling, superstitious theocracy that has forgotten how most of its own technology works. It doesn't invent anymore — it prays over ancient machines and hopes they keep working. (The tech-priests of the Adeptus Mechanicus literally chant litanies to repair a gun.)
- The God-Emperor. Ten thousand years ago the Emperor — a near-immortal being who had guided humanity since antiquity — was mortally wounded saving the species (more on that below). Now he sits on the Golden Throne, a rotting half-corpse, neither living nor dead, kept "alive" by sacrificing roughly a thousand psychic humans to him every single day. He is worshipped as a literal god. The Emperor protects.
- The look. "Gothic-industrial": cathedral-spaceships, skulls and incense everywhere, candle-lit terminals, parchment and Latin-sounding prayer alongside chainswords and laser rifles. Trillions live crammed in mountain-sized hive cities. Imagine a medieval Inquisition that has spaceships.
A solid beginner lore video covers the backbone of all this. It tells the Imperium's origin chronologically and then jumps back through the timeline: the Emperor builds super-soldiers called Space Marines and twenty god-like Primarchs to reconquer the galaxy, then his favorite son Horus is corrupted by Chaos and turns half of them traitor. That galaxy-wide civil war (the Horus Heresy) is the climax — it's how the Emperor ended up dying on the Throne. Everything in our one-shot happens 10,000 years after that, in the grim present. You don't need more than that.
The Tone — Grimdark (and What It Means for Playing)
Grimdark is not "edgy for its own sake." It's a specific register, and getting it sets the whole mood:
- No clean victories. A "win" means a world survives at horrific cost, or a threat is delayed — never truly beaten. Success here is "we held the line, and most of us died for a reason." Aim for that, not for saving the day.
- Faith and fear. Ordinary people endure misery through religious devotion and terror of what's outside the walls. Hope is a luxury; duty and sacrifice are the virtues that count.
- Grim, but knowingly over-the-top. The setting knows it's absurd — skulls on everything, gothic melodrama, gallows humor. So it's fine to be a little operatic and to laugh at the bleakness. The register is grim resolve under fear, shot through with dark comedy — not swashbuckling, not winking parody.
Think Dune meets Event Horizon meets a medieval witch-hunt. Bleak, baroque, and blackly funny.
The Big Threats
Chaos & the Warp — the enemy within. The Warp (a.k.a. the immaterium) is a parallel hell-dimension made of raw emotion and nightmare. It powers faster-than-light travel and gives psykers (this universe's wizards) their powers — but it's home to demons and the four Chaos Gods, each born from a mortal feeling:
| God | Domain |
|---|---|
| Khorne | rage, blood, slaughter |
| Nurgle | disease, decay, despair (with a grandfatherly "love") |
| Tzeentch | change, scheming, sorcery, ambition |
| Slaanesh | excess, pleasure, obsession |
Mortals who give in become Chaos cultists or Chaos Space Marines (the original traitors, still at war 10,000 years later). Chaos is the heretic next door, the whisper in your own head. It is the thing the Imperium fears most — because it's already inside.
The xenos (aliens), at a glance:
- Orks — savage green fungal brutes who live only to fight. Numberless, crude, gleefully violent. Their tech half-works because they believe it will.
- Tyranids — an extragalactic hive-mind swarm that strips a planet of all life and moves on. Alien crossed with locusts.
- Necrons — ancient skeletal robot-undead waking after 60 million years to reclaim the galaxy. Cold, methodical, nearly unkillable.
- Aeldari / Eldar — a dying, arrogant elder race of master psykers; few, but terrifyingly advanced. (Their sadistic raider cousins are the Drukhari.)
- T'au — the youngest race: idealistic, high-tech, communal optimists expanding under "the Greater Good." In this galaxy, optimism reads as dangerously naïve.
Who You Are
For a one-shot, you're almost certainly mortal humans (or their elite enforcers) — a small band of the competent-but-killable against impossible odds. The classic archetypes:
- Imperial Guardsman (the Astra Militarum) — the ordinary human trench soldier, expendable by the billion. The backbone of the Imperium.
- Space Marine (Adeptus Astartes) — 7-foot genetically engineered super-soldier in power armor. The iconic poster-boys.
- Inquisitorial agent — an investigator of the Inquisition with near-unlimited authority to hunt heretics, mutants, and aliens; often leading a ragtag warband (assassins, psykers, tech-priests, hired scum).
- Plus: Sisters of Battle (militant nuns), Tech-Priests (cyborg engineers), Ministorum Priests (war-preachers), Rogue Traders (licensed merchant-explorers).
What your character believes (this is the important part): A loyal subject of the Imperium knows three things in their bones —
- "The Emperor protects." He is a literal god. You pray constantly and live in pious dread.
- Suffer not the witch, the mutant, the alien, or the heretic. Any deviation is damnation. Psykers especially terrify you — a witch can let demons in.
- Ignorance is a virtue. "Blessed is the mind too small for doubt." Curiosity is dangerous. You believe your suffering and obedience are literally what hold the darkness back — and in this universe, that's true.
How to Roleplay Here — 5 Quick Tips
- Play zealotry and dread, not heroism. Quote scripture, salute the Emperor, distrust outsiders. Your characters aren't quippy adventurers — they're frightened, faithful people doing a terrible duty.
- Treat any witchcraft or mutation as a death-sentence threat. Reflexive suspicion is correct in-setting. A glowing-eyed stranger isn't intriguing — it's a heresy to be reported (or shot).
- Distrust your own power. Using psychic abilities, ancient tech, or making deals invites corruption. The setting punishes the easy path — lean into that tension.
- Embrace the gothic gravity — then crack a grim joke. Formal, ritualized, fatalistic speech is the default; gallows humor is the release valve. Both belong.
- Remember the scale. Your squad is one candle against an endless night. The goal isn't to win the war — it's to do your duty and matter for one moment. That's the whole point of the genre.
Your Character Lives Here
You are one small life on one of a million worlds, in the ten-thousandth year of a war that will never end. The sky is the wrong color from the smoke of forge-stacks; somewhere a vox-speaker is reciting the names of the day's executed heretics. You pray to a god who is a dying corpse on a golden throne, and you mean it, because your faith is one of the things actually holding back the demons. Tomorrow you may die for a hill, a hab-block, or a sealed door no one will remember — and if you die well, that is enough. There is no rescue coming. There is no better future on offer. There is only the duty in front of you, the people beside you, and the dark pressing in.
Hold the line. The Emperor protects.