Mothership vs Alien RPG - which sci-fi horror game fits your table?
The short answer
Pick Mothership if you want a lean sci-fi horror kit and you want to build the nightmare yourself. It hands you a d100 engine, four blue-collar classes, a stress track and a Warden's manual full of procedure, then steps back. There is no canon to respect and no licence telling you what is in the airlock.
Pick Alien RPG if you want to play inside the films. Weyland-Yutani, xenomorphs, Colonial Marines and the whole ugly corporate machine are already written down, and the cinematic scenarios are built to start and finish in a single evening, usually with a body count.
What these two games have in common
Both are science fiction horror about working people in cheap ships a long way from help. Nobody is a hero. You are contractors, crew and colonists, people who fix things for a living and who signed something they did not read closely. Both games assume your character will probably die, and both treat that as the design rather than a failure.
They also share a bloodline. Mothership grew out of the same truck-drivers-in-space aesthetic that Alien invented in 1979, and both track psychological pressure with a number that climbs. In each game it is that number, not the creature, that finally undoes you. The question is not which universe you prefer, but how much of it you want handed to you.
Where they really differ
The dice. Mothership is a d100 roll-under game. You roll percentile dice against a Stat (Strength, Speed, Intellect, Combat) or a Save (Sanity, Fear, Body, Armor) and you want to land under it. Fresh characters hover around thirty to forty percent, which tells you what kind of week this is going to be. Alien RPG runs on Free League's Year Zero Engine: build a pool of six-sided dice from an attribute plus a skill plus your gear, and every 6 is a success. One difference outweighs the maths. In Alien you may push a roll and try again, and pushing costs a point of Stress. In Mothership there is no second attempt, only the consequence.
Stress. Here the two games stop looking alike. In Mothership, Stress is pure debt. It climbs when you fail, and a critical failure triggers a Panic Check: roll the d20 panic die, and if it lands equal to or under your Stress you go to the panic table and stop being in charge of your own character. You bring it back down with rest and shore leave between jobs. In Alien, Stress is a bargain. Each point adds an extra die to your pool, so a terrified character is genuinely more likely to hit the shot. But if any stress die shows a 1, you make a Panic Roll: a d6 plus your current Stress, read off the panic table. The Evolved Edition takes some sting out of that with Resolve, a value drawn from Wits and Empathy.
Who owns the monster. Mothership includes a bestiary, Unconfirmed Contact Reports, but its real gift is a set of tools for designing your own horror. Sean McCoy has said outright that there is no canonical Mothership beyond the one happening at your table. Alien RPG is deliberately the opposite. The xenomorph life cycle is statted, Weyland-Yutani has departments and motives, and the Evolved Edition adds the Tartarus Sector to campaign in. That is a gift if you want the films and a wall if you had your own idea.
What you do before the session. Mothership's Warden's Operations Manual is a manual for making things: threats, stations, factions, jobs, one-page prep you can finish on the train. Alien scenarios arrive finished, written as cinematic adventures with acts, timed events and a sealed personal agenda for each player. Your prep is reading and pacing, not building.
How long it lasts. Alien has two official modes. Cinematic play is a one-shot or two-session story with pregenerated characters, agendas that pull against each other, and a survival rate that suits the source material. Campaign play uses your own crew over months. Mothership has no mode switch. Its default is the job-to-job loop of contract, disaster, shore leave and debt, and it quietly counts how many sessions a character has lived through.
What it feels like at the table
Mothership feels like a bad shift that will not end. The Warden describes a corridor, someone rolls to force a jammed door, the dice come up wrong, Stress goes up by one and nobody says anything. Twenty minutes later the marine fails a Fear save at the worst moment, the panic die comes out, and the table watches a competent adult do something stupid and irreversible. The horror is procedural. By the time you understand the shape of the thing on the station, two of you are already gone.
Alien feels like the third act of a film you have seen. The Game Mother hands out agenda cards and suddenly the science officer will not say why she wants the specimen intact. You roll a fistful of d6s for the door release, you push because you have to, and one stress die comes up a 1. Panic roll. The pilot empties a magazine into the dark and now the corridor knows where you are. It is loud, fast, betrayal-shaped, and it ends the evening it started.
What you actually need to buy
For Mothership, one purchase does it. The Mothership Core Set (EUR 59.95) is the complete first edition boxed set: Player's Survival Guide, Warden's Operations Manual, Unconfirmed Contact Reports and Shipbreaker's Toolkit, plus the introductory adventure Another Bug Hunt, dice including the panic die, pawns, a poster map and a Warden's screen. If you know you want the whole shelf, the Mothership RPG Deluxe Set (EUR 99.95) adds the modules Dead Planet, A Pound of Flesh and Gradient Descent in full colour. Hull Breach Volume 1 (EUR 44.95) is optional and third-party, an anthology of twenty-six adventures and toolkits.
For Alien, choose your door. The Alien RPG Evolved Edition Core Rulebook (EUR 44.95) is the whole game in one hardback: life path character creation, revised stress and panic, reworked combat, the Tartarus Sector and a solo mode called Last Survivor. The Evolved Edition Starter Set (EUR 29.95) is the cheaper way in, with abridged rules, five pregenerated characters, custom dice, maps and the scenario Hope's Last Day. Rapture Protocol (EUR 39.95) is a cinematic scenario and needs a core rulebook rather than replacing one. The MU/TH/UR screen (EUR 24.95) is comfort, not a requirement.
Choose Mothership if ... / Choose Alien RPG if ...
Choose Mothership if your favourite part of running a game is designing the thing in the dark, and a monster with a trademark would spoil it. Choose it if you want to prep a whole session in half an hour and still surprise yourself. Choose it if your group likes fast, merciless resolution and rolls up a new crew member without mourning. Choose it if you want an engine you can bolt any science fiction idea onto, from a mining strike to a salvage job that should have been simple.
Choose Alien RPG if you want the films, with the names and the shapes and the corporate letterhead, and a game that only gestures at them would disappoint you. Choose it if your group never finishes campaigns and would rather play one complete, ruinous story in an evening or two. Choose it if you want a rulebook that answers questions instead of asking them. Choose it if you like a system that rewards fear as well as punishing it.
One honest aside. If what you really want is investigating the unnatural in the present day rather than in deep space, neither of these is your game and Delta Green serves you better than either.
Where to start at Netherbook
For Mothership, start with the Mothership Core Set, and read our Mothership starter guide first if you want a feel for the panic die before you commit. The rest of the line, including Hull Breach Volume 1, sits in the Mothership collection.
For Alien, start with the Evolved Edition Starter Set for the cheapest honest test of whether your table likes it, or go straight to the Alien RPG Evolved Edition Core Rulebook if you already know you do. Our Alien RPG starter guide walks through the first session, and the rest lives in the Alien collection.