2400 devlog: Orbital Decay

Orbital Decay is a one-shot space horror scenario generator. It was the first 2400 game to include a map, four broad skillsets, stress rules, and guidelines for creating and running scary monsters. Get it as part of the entire 2400 collection on Itch.io, and on its own and in the 2400 bundle on DriveThruRPG.


I suspect it’s obvious that Orbital Decay was inspired by Mothership and Alien, but just to be transparent: I wrote this game to run Mothership adventures, and I was totally shameless about it.

The setup for Orbital Decay — being marooned in space and needing to explore to fix your jump drive? Stole it from Dead Planet.

That little bit on the back page, where it says, “If they leave without dealing with the creature, it — or other consequences — will follow”? Ripped it off directly from The Haunting of Ypsilon 14.

Just shameless. Go buy some Mothership adventures so I feel less guilty. They’re really good. I’m especially fond of Dead Planet (which I’ve run with 2400 and Mothership rules) and A Pound of Flesh (which I’ve played with Offworlders). And you should absolutely just crib the hacking rules from their Hacker’s Handbook if you want something more in-depth for Inner System Blues, Resistors, or others.

I get why other people like the Mothership rules, but they (or at least their earlier, pre-Kickstarter version) didn’t really hit the spot for me. I hear that the newer version addresses my biggest complaint — too many rolls and too much whiffing in combat — but still, I wanted something even more lightweight. And I don’t like rolling two d10’s for resolution, or four d10’s when you have an advantage. I’m a picky pain in the butt that way, and I don’t blame Mothership for it.

As I mentioned in passing here long ago, the most immediate precursor to 2400 was a minimalist Knave hack for Mothership adventures I called Dropship. It was so unimpressive that I never shared it online (which is good, because now that name is being used for a much better minimalist Mothership hack). I shifted my attention to designing a different kind of system — 2400 — but I felt like I needed to establish some other sci-fi keystones before I could get back to Mothership-style horror.

Hacking the skill list

While Mothership has a very extensive and granular skill list, it also influenced the shorter list of skillsets in Orbital Decay. I expected to use this game mostly for one-shots, so I wanted character creation to go very, very quickly. And so, to discourage over-analysis during character creation I collapsed everything into four skills — three of which designed around the Mothership classes.

Other 2400 games with broad skillsets tend to split up combat into Strength and Speed; Orbital Decay bundles all combat into a single Security skillset to reflect the Marine class in Mothership, and to make sure people who get anxious about combat know exactly what to take if they want to reduce their likelihood of dying in an admittedly deadly module.

And while other 2400 games collapse technical skills into Tech, Reason, or Logic, Orbital Decay splits them into Science (reflecting Scientist class) and Maintenance (reflecting the Teamster class, which makes clear you’ll be good at physical labor, like prying things open with crowbars). This makes it more likely you’ll get at least one player capable capable of fixing your ship for this particular scenario, and you don’t necessarily have to be trained in combat to face physical challenges.

The fourth skillset is Command — a social skill. It has lower utility in this specific scenario, as you’re unlikely to encounter many people who actually want to talk, but I didn’t want players to feel unable to socialize if they keep playing after this scenario. To try to make Command more obviously useful here, though, I explicitly said that you can use it for “inspiration.” Using the help rule, that means you can roll your Command die to benefit pretty much any roll by any teammate by giving advice, watching their back, or cheering them on. I hope that makes it much more useful — and I hope I didn’t imply that too subtly.

All of that said, in retrospect, I think the more granular approach to skills would probably work even better in Orbital Decay — it would lead to more frequent disasters, befitting a horror scenario. If you want to run Orbital Decay that way, I’d recommend picking two skills from the ones alluded to in the broader skillsets, assigning d10 to one and d8 to the other (e.g., a character in a Maintenance role might take d10 in Labor and d8 in Repair).

Evoking horror

I’ve read a lot of different takes on “how to do horror in RPGs.” I think there’s more than one fair answer. Some options include…

Creepy fictional elements like people, places, and situations that are unnerving, out of place, and/or unexplained, like in Dead Space and Prey. (A child’s birthday party looks light and fun until you put it in an abandoned space station where everybody else you’ve encountered is a corpse.)

Inducing dread through procedures or rituals, like pulling Jenga blocks in Dread and snuffing out candles in Ten Candles.

Loss of agency enforced through rules, like critical damage in Into the Odd and panic rolls in Mothership.

I have never had a good idea for how to do the second of those, but I figured I could handle the first and the third in Orbital Decay.

My first stab at a “loss of agency” mechanism inspired by Mothership’s stress rule was misguided, and I’m ashamed to say I published the game before catching it. That version had a list of almost 20 “stress effects” that might happen when you use an ever-increasing “stress die” to improve chances of success on a roll — basically, trading one risk for another. Some of those effects were long-term, and the advancement system required you to suffer a long-term stress effect to increase a skill. As one playtester noted (and as acknowledged in a follow-up devlog), I was basically gamifying PTSD. I really, really didn’t want to do that.

After this revelation, I redesigned the stress rule. I took out the permanent stress effects and the hook into advancement rules, and collapsed the stress effect list into fewer options, dramatically increasing the likelihood of the result that worked best in playtesting. Now, on a 13+, “you see, hear, or realize something that no one else perceives [which] may or may not be real, at the GM’s discretion.”

The wonderful thing about this solution, I found in playtesting, is that it does triple-duty.

Creepy fictional elements: The character perceives something unnerving and out of place, like seeing somebody who killed rising from the dead.

Loss of agency: The player still gets to play their character, but their body or mind rebels against them. Some stress effect results are just a momentary loss of agency (like: “Scream, unbidden and animalistic, loud enough to attract attention”), but the highest results are especially treacherous because the player can’t tell whether what their character is perceiving is real or not. And if it is real…

Moving the action forward: If the character is just hallucinating or seeing “ghosts,” that serves to instill a sense of creepiness appropriate to horror. But if they’re not just hallucinating — if they actually are experiencing some kind of “dread insight” — they now know something that may be critical to understanding the situation they’re in, and perhaps even how to get out of it.

Honestly, I wonder if those dread insights ought to start even before you break out the d20 stress die. It’s the most fun part of the game to me. (Edit to add: Yeah, I went back and edited it, cutting out some results that felt redundant in play and making the dread insights show up on 11+.)

Creature design

People and creatures controlled by the GM don’t really have “stats” in 2400, or even skill dice. The GM doesn’t roll for them. The procedure of the game calls on the GM to describe what the players perceive about the world, and it calls on the players to describe how they react to (or act upon) what they perceive.

I typically find this a lot easier to run as a GM than to think of my characters symmetrically with the players: It’s tough to keep track of a bunch of characters that each have the same level of detail as a single player’s character, but easier (for me) when approached as tracking “the fictional context” as more of a unified state. But that’s so unlike what you’re probably used to doing in other RPGs — especially D&D — that I know it can be a tough shift if you already have a bunch of GMing experience under your belt.

So, Orbital Decay is meant to demonstrate how the GM can present a “big bad” enemy. Here, I described it as “behavior” and “defenses,” but I think it’s better explained in Battle Moon as behavior that demonstrates motivations, risks that it presents to the players’ characters, and obstacles that might prevent it from being dispatched in a single roll.

(Yes, in 2400, if a target doesn’t present any such obstacles, you can dispatch it in a single roll! It just might be riskier than breaking it down into smaller steps.)

Behavior (if I may quote from my own later game) simply describes, “What do they do to get what they want?” Orbital Decay offers four examples to explain why the creature is going to try to kill the characters (because it will try to kill them). It surely isn’t an exhaustive list.

Risks are what might happen to a character if they roll in a conflict with the creature. In Orbital Decay, some of these are bundled under “defenses,” and include things like a paralytic stinger or telekinesis. But even if you happen to roll only purely “defensive” defenses (like “exoskeleton” and “psychic screen”), being close to a creature intent on murdering you could risk being attacked with teeth, claws, or whatever sharp objects it can find handy.

Obstacles are things that prevent you from dispatching the target in a single roll. They’re kind of like “hit points,” but with a narrative justification for each. Creatures in Orbital Decay have a number of biological adaptations that can endanger the characters, and each must be stripped somehow in order to defeat it.

I think I made a mistake in describing those obstacles in terms of “defenses” in the earlier versions, a player-facing term. (I went back and edited it, so now they called “obstacles” instead.) Yes, they do act like defenses, both in literal terms and in game terms — things you can sacrifice to negate the effects of an unfavorable die roll, just as players can declare their armor broken. But as a player, it is really, really not fun to be told, “Yeah, sorry, your awesome roll doesn’t count because I’m breaking my armor as defense.

I think it’s more satisfying for players to present obstacles in the way described under the dice results in the “Rules” column: “If success can’t get you what you want (you make the shot, but it’s bulletproof!), you’ll at least get useful info or set up an advantage.” And in Orbital Decay, the most welcome info you can receive is that you’re one step closer to defeating this thing that’s trying to kill you.

The map

I think this might be the first map I ever designed for a roleplaying game. I’d probably doodled some flow charts for a point crawl or rough dungeon layouts to use at my own table, but this was the first, like, map. I suspect it’s not very good!

I think I might agree with Chris that the space could’ve been better spent on more ideas. I probably could’ve condensed that whole page down to a couple sentences, like:

The BRIDGE is in the front of the ship, followed by a CENTRAL CORRIDOR that runs its length, passing through the DOCKING BAY, between two ESCAPE PODS, between the CAPTAIN’S QUARTERS and CREW QUARTERS, between the MEDICAL BAY and GALLEY, to the CARGO HOLD, which then connects to the CRYO BAY, ENGINEERING, and LIFE SUPPORT in the back of the ship. Adjacent rooms can also be accessed by MAINTENANCE DUCTS, which also wind through the wings of the ship.

I don’t remember what I put in the text-only version of the game. It was a little longer than that, I think. It took me a lot longer to write. But I could’ve put in whatever I put in there, or the thing I just busted out in under a minute above, and used the rest of the page for other things. Maybe put the stress effects on the interior, where they’d be player-facing, and still have some space left over for more character options, even if only to set up personalities. Free up some space on the back for a table of hallucinations, or people you might wake from cryo, or way more creature behaviors and abilities.

But I’d never made a map before, and I wanted to try. So you got a map.

Combining with other 2400 games

Orbital Decay is meant to be able to stand on its own as a one-shot, but I also see it as a good starter scenario for a multi-session arc. Here are some suggestions for how you might combine it with other modules.

Horror scenarios in any 2400 game could make use of Orbital Decay’s stress die rule. I find it trivially easy to run Mothership scenarios with 2400 now, too; when a module prompts you to make a stress roll, the player skips right to rolling their stress die on the stress effects list.

Monster-fighting scenarios in any 2400 game might also benefit from the creature tables, or using these tables as templates to create your own creatures. I could see this coming up most frequently in Data Loss, Exiles, Xot, Zone, Eos, Xenolith, Legends, and an extra-special main event in Battle Moon.

If the characters survive Orbital Decay and continue into an ongoing game, they’re going to need a ship! I recommend bring over the ship options from Cosmic Highway, inviting each player choose 1 upgrade they imagine their character might make use of. You might also want to give them a crew (maybe from Eos). If you want to deck out the derelict with fun gear to loot, you’ll find more options in Inner System Blues.

And finally, the advancement rules for Orbital Decay aren’t even really rules, so much as a single milestone: survive this scenario. If the players do survive, you’ll need another rule for when they advance next. Consider using the rules from Cosmic Highway or Eos, depending on what kind of crew it is. If you want to offer more advancement options, throw in talents from Eos and/or Legends as advancement options. And if you want to slow down advancement considerably, any new skills they raise to d8 have to be the granular skills seen in Cosmic Highway, rather than the broader skillsets they get to choose from in Orbital Decay.

Featured image edited from original by Beeple (Mike Winkelmann).

3 responses to “2400 devlog: Orbital Decay”

  1. […] I tried to carry this philosophy through the material on the back page as well. Dark Souls “boss fights” can feel like a tedious grind to whittle down their hit points before they whittle down yours … but not when they’re fun, I think. I personally think they work best when you’re able to approach them as puzzles: sussing out the enemy’s logical weaknesses, observing the patterns in their behavior to exploit openings, spotting what in the environment you can use to your advantage. The metaminds of Data Loss are thus my attempt to boil down video-gamey boss fights to fictional rules, using the same considerations of risks and obstacles I tried to introduce with explicit examples in Orbital Decay. […]

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