2400 devlog: Eos

Eos is a microgame about humanity’s entry into a diverse galactic community, seen through the eyes of a crew that’s expected to serve as soldiers, explorers, and diplomats alike. You can get Eos as part of the entire 2400 collection on Itch.io, and on its own and in a bundle on DriveThruRPG.


Eos is the second Mass Effect homage in 2400, alongside Xenolith. (It’s also a fine setup for a Star Trek game, which I think reflects Mass Effect’s influences.)

You can certainly play either Eos or Xenolith alone — but to me, they’re two halves of the same game, only broken up because I had too many ideas for “how to do Mass Effect in 2400” to fit them all in a single three-page game. In fact, I considered designing them as a single, double-sized microgame, but I decided I wasn’t ready to break the 2400 format that dramatically just yet. (And when I do break it, I’d prefer to break it for an entire book.)

So, while Xenolith covers the “aliens” side of my Mass Effect homage, Eos covers the “humans” side. Some major points of influence…

The setup as a crew of soldiers/explorers/diplomats, whether they like it or not, is pretty obviously inspired by Mass Effect’s Normandy (but again, that’s not that different from the Enterprise).

The technology includes a “holo-tool” (inspired by Mass Effect’s omni-tool) and a “holo-shield projector” (inspired by the kinetic barriers standard to Mass Effect characters).

Bonds are inspired by the “loyalty missions” in the Mass Effect series, and the pacing of the Mass Effect series as a whole. Eos’s rule for increasing bond dice — narrating how you spend time with a crewmate during downtime between missions — mirrors how Mass Effect games see you alternate between action/adventure gameplay and social interaction gameplay.

The crewmates controlled by the GM aren’t based on any particular characters in Mass Effect, but were designed by asking myself, “If I had to write characters for a new Mass Effect game, who would I put on the ship?” The roles would need to include a pilot, a captain, an engineer, a doctor, and so on. A good mix of personalities should include people who are quiet, people who are funny, people who are lovable, and so on.

The missions are explicitly designed to offer the kinds of moral quandaries you find at the end of Mass Effect missions (and some of my favorite Star Trek episodes). This is a game not just about exploring space, but making tough calls once we get there.

Talents take their name and concept from the term used for character abilities in the first Mass Effect. These represent not just ways of getting quantitatively better at something, but qualitatively better. And they make “leveling up” a bit more fun. Mechanically speaking, these represent something of a departure from other 2400 games — and also my biggest challenge in designing Eos.

Talent design

Coming up with superhuman powers, helpful mutations, and beneficial alien traits are easy enough for me: They expand the range of what a person can do. Having wings or telepathy is self-evidently useful. I don’t have to explain much more than that one word (unless I feel it’s necessary to somehow set parameters, like specifying that you can’t telekinetically throw a car without endangering yourself).

Coming up with qualitative talents based on mundane abilities, however, is much more challenging for me, especially in the context of a game that already has pretty granular skills. When you get better at marksmanship, you increase the Shooting skill — so what does a Sharpshooting talent even do? In a video game, it might grant more quantitative bonuses that are thankfully managed by a computer, hidden under the hood. In a tabletop RPG, more mechanical tweaks become more burdensome.

I thought of multiple ways to handle these sorts of questions. And the talents in Eos are meant as not a definitive list, but as examples you might use as templates. Here’s how they might be broken down:

REDUCED RISK: [Do a pretty specific, challenging thing], no roll needed.

Examples: Filching (pickpocket or palm a small object in plain sight); Blending In (be invisible in crowds, shadows, and ductwork).

Use for fairly narrow actions that would make the character seem extra-cool, or for “always-on” abilities, like always being able to tell when somebody’s lying. Don’t use for actions where skipping the roll might be anticlimactic or send a message you don’t want to send to the group. The way I run 2400, at least, violence is almost always risky; I wouldn’t make a talent that routinely skips most combat rolls.

SHIFTED RESULT: When [doing a thing], treat disasters as setbacks, setbacks as success.

Example: Intrusion (“when bypassing security”).

This is a variation of the “reduced risk” template above, but slightly less powerful — it’s effectively an arithmetic-free way of saying you get a +2 bonus, but unlike with “reduced risk,” you do still need to roll. Accordingly, talents constructed with this template might be broader: “bypassing security” could mean picking a lock, hacking a computer, looping the feed on a camera, etc.

INCREASED EFFECTIVENESS: [Achieve an impressive result] as easily as others [use the same skill less impressively].

Example: Sharpshooting (“fire trick shots or at multiple targets as easily as others pull a trigger“).

This is another variation of “reduced risk,” but framed as an invitation to set more ambitious goals without taking on as much risk as less talented characters might. Use this for actions anybody could attempt, but that have an obvious and broad range of possible results depending on skill. Or, to put it another way: Use this for actions you want players to describe with a bit more flair.

BONUS EFFECT: When you roll a 3+ [doing a thing], [something else cool happens].

Example: Martial Arts (follow hand-to-hand rolls with a throw, grab, disarm, etc.).

This is a more specific variation of “increased effectiveness.” Use for actions that have obvious and interesting follow-up maneuvers.

RULES EXCEPTION: When you [engage with this particular rule], [break the rule a tiny bit].

Examples: Close Protection (when you help, your friend doesn’t have to suffer the risk); Jury Rigging (when you break a thing, it doesn’t become useless — at least not right away).

There aren’t a lot of rules in 2400, but the ones that are there are meant to be broken, right? Use for things that slot easily into those few rules that are there.

SKILL SUBSTITUTION: Use [a skill] to [do a thing] instead of [the usual skill you’d use for that].

Example: Sabotage (use Electronics to attack instead of Hand-to-hand or Shooting).

This kind of talent works best when you play with a more granular skill list. Use to give players an excuse to roll less-used skills more often, but make sure the talent provides clear fictional justification. (Sabotage, for instance, specifically only attacks electronic targets, or targets carrying electronics.)

SELF-HELP: Roll [skill] to help [a certain kind of roll].

Example: the Force Multiplier power in Project Ikaros, and the Enhance mod in Data Loss (use telekinesis skill to help athletic feats).

This is basically a souped-up take on skill substitution, allowing you to roll two skill dice at once. While the examples above come from a superhuman power, there’s no reason you couldn’t use this construction for mundane talents. If you want to have this kind of talent alongside skill substitution talents, consider narrowing what self-help might apply to. You may be able to enhance all athletic feats with a superpower like telekinesis, but perhaps your medical knowledge only specifically helps you in hand-to-hand combat against human beings (with thanks to Robert Downey Jr.’s portrayal of Sherlock Holmes for that example).

SELF-SACRIFICE: Accept or worsen a hindrance to [do something extraordinary].

Example: Nosebleed (accept or worsen a hindrance to amplify the effects of a psychic skill roll).

This could be formatted a couple different ways, specifying some other resource to spend or item to break in order to achieve the effect. (It’s phrased this way because I don’t like tracking lots of abstract currencies, though.) Because it actually requires accepting some kind of penalty or expenditure, whatever effect the character achieves should be pretty amazing. Nosebleed lets you amplify psychic skill rolls, which is open to interpretation, but I picture it being used to hurl a car instead of a basketball.

SPECIAL DEFENSE: Break [something easily replaceable] as defense.

Example: Barrier (break your always-on telekinetic field as defense).

That particular example is a superhuman power, but there’s no reason it has to be. You could reskin that exact same talent as a functionally identical combat talent called Defensive Stance, which can be broken as defense once per fight.

NEW CAPABILITY: You can [do a thing humans can’t normally do].

Example: Holography (you can use your smartphone to create illusions).

This kind of talent is easiest to conceptualize in terms of superhuman powers and special equipment, but it you can also think of it in terms of allowing a human to do something quickly, or with ease that would be hard to do even with the right equipment.

Some (probably even all) of those bullet points are basically just reusing concepts outlined by other games. Looking back over it, I recognize things like “skill substitution” as one of the guidelines for making stunts in Fate Core, and “reduced risk”/”increased effectiveness” are basically the “position” and “effect” logic from Blades in the Dark. (The whole procedure of play leading up to the roll in 24XX basically is negotiation for position and effect, but I avoid ever using those terms that way because it can feel a little daunting to formalize it so strictly.)

As far as I’m concerned, any of the talents in Eos could’ve been designed using any of the other talent approaches described above. Martial Arts could be phrased like Sharpshooting, saying you combine a block, grab, and throw as easily as others throw a punch. Filching could have you turn disasters into setbacks, and setbacks into successes. Sharpshooting could give you a bonus effect on a 3+ roll. I was purposeful with the solutions I did use for each one; I thought skipping the roll for picking a pocket would be fun, for instance, while skipping the roll for firing a weapon might feel anticlimactic. But I hope it’s clear that this list isn’t gospel — it’s a starting point.

(Thanks to Remi Garreau for helping me phrase these templates better!)

Combining with other 2400 games

As I describe at some length in the Xenolith devlog, Eos is designed so it certainly could be part of the same setting as any or every other 2400 game — but when I run it, it only and always shares its setting with Xenolith. That said, there’s still plenty from other 2400 games you can port into an Eos game, and some tidbits from Eos you can use in others.

For alien characters, you can roll on Eos’s back page, and/or use the “Species” page from Xenolith. Specialties from either game would work fine for Eos characters.

For more ship options, bring over the ones from Cosmic Highway, inviting each player choose 1 upgrade they imagine their character might make use of.

For more gear options, including cybernetics, check out Inner System Blues.

For more “talents” — whether by exporting Eos’s list to another 2400 game, or bringing more options into Eos — combine with the warrior and rogue talents from Legends, the list of psi powers from Project Ikaros, and/or the “mods” from Data Loss (with arcwire mods as acting as Mass-Effect-style “tech powers.”) If introducing talents to a 2400 game that doesn’t normally feature them, you could hand out the list (or an edited version thereof) when the players first advance, or welcome them to replace a skill increase with a talent during character creation.

If you want a shorter skill list, consider using the one from Orbital Decay, Data Loss, or Legends instead, or just use the talent categories from Eos itself: Combat, Espionage, Influence, Technology, and Psi. This makes it much more obvious during advancement when you “qualify” for a talent.

Be advised, however, that different skill systems will change the “exchange rate” of talents, so to speak. You get more out of increasing a broad skill like Strength (like in Data Loss) than out of increasing a narrow skill like Hand-to-hand, Climbing, or Labor, but Eos’s advancement system doesn’t distinguish between these when saying you can take a talent instead of a skill increase when you advance. If this bothers you, and you want to advance more slowly, you may wish to say that you need to complete three missions to advance a skill, instead of just one.

To use “bonds” in other 2400 games, just bolt the rule on. And take a look at 24XX Bandit by Adam Schwaninger for another approach to this rule that might decrease confusion at the table: Instead of offering an extra die when helping an ally, you just roll your bond die, regardless of skill. (I prefer to avoid “bonus die that changes size” rules because it can lead to confusion about what “d8” means on your sheet — bigger die, or bonus die? — and Adam’s solution is a tidy one.)

For stress rules — in case you want to use Eos for something like a Mothership adventure, or want to play up the mind-altering affects of the alien artifacts in Xenolith — check out Orbital Decay.

For more in-depth combat rules guidance, check out Battle Moon and Emergency Rules, and Data Loss for examples of how you might set up video-game-style “boss fights” that work like problems to be solved.

For more people, places, missions, and twists, combine the back pages of Eos and Xenolith (and maybe throw in some from ALT while you’re at it — secret agent missions should fit in okay too).

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

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