Messing around with Momentum (plus a rough draft adventure game system)

02 Nov, 2026

A while back I posted about using a usage die system with hit dice as a replacement for hit points, called the Vigor die, and in that I mentioned I had a "weirder" version of the Vigor die I was messing with that I'd post about later. Well, it's later now.

The Goal

While working on my fantasy spacefaring adventure game Aethernatus (I'll post about that later), I got really into the idea of trying to capture momentum as a concept, specifically for "action scenes." Fights, chases, high-stakes situations where every second counts, that sort of thing. At the same time, I was pretty enamored with expressing the difficulty and risk of an in-game action without using numbers or extra dice, and I wanted to see if I could take that a bit further, with no numerical stats or skills at all, in a way that I liked better than how Quest and Salvage Union do it.

So, two goals:

1. Capture the feeling of in-game momentum during play.
2. As few numbers as possible.

The result is something I like, though not for Aethernauts, which I want to be paced differently than the experience this system produces. (That one's likely headed down the Mark of the Odd path, mostly.) But I do still like it, and so I want to keep experimenting--and I want to share it. It uses an adaptation of the Bastionland action procedure along with constantly shifting step dice and a complete lack of numerical attributes. There are still plenty of unanswered questions, too, so what better place to put an unfinished mechanic that may or may not be based on a completely unworkable premise than a blog post?

So, here it is. This is maybe the Momentum System, or the Swing System, or more likely neither of those. I'll include some of the flavor, too: it's in the setting I'm developing for Aethernauts, but decades before that game, during the initial rush to the stars.

I am, as with all things I post publicly, very open to feedback, should anyone be interested enough, because of course I want to yap about my game as much as I can. (And if someone actually tests this out themself, please tell me, I'll be so stoked.)

Taking Swings with Troubleshooting Stars (Working Title)

An adventure RPG for three to five players. One player is the Referee (Ref). The others play as Player Characters (PCs) who are part of a crew of troubleshooters who sail the aether among the celestial spheres, solving expensive problems on behalf of trading companies mining the constellations for valuable solid quintessence, called Shine. Aether travel is still young, but this absurdly lucrative Shine Rush has invited plenty of trouble that needs shooting, and you might as well get yours while the getting's good.

Attributes

A PC has two core attributes, both measured in a die size: Vigor and Momentum.

• Vigor. Overall wellbeing. Starting and max Vigor is d8. Reduced by harm and fatigue.
• Momentum. Initiative, focus, morale. Starts at d6, with a maximum of d12 and minimum of d4. Increases when you succeed at risky actions, decreases when you stumble.

These attributes can be stepped up (increase by 1 size) or stepped down (decrease by 1 size). If Vigor goes below d4, suffer a Wound (see Harm & Wounds). If Momentum goes below d4, suffer Pathos (see Pathos).

Taking Action

When a PC takes action, discuss the action procedure as a table:

• Intent. What is the PC doing and what are they trying to achieve?
• Position. Can they do what they intend? Consider their traits and gear, along with the fictional situation. Are they on the back foot? Will this cost them something?
• Risk. Based on the intent and position, is the outcome uncertain? Is there something at stake? If there’s no uncertainty or nothing at stake, don’t roll, just do what makes sense. If there is, make an action roll.
• Impact. Show what happens as a result, play out the consequences, and then continue.

A PC’s features, like traits or gear, might mean they don’t have to roll where another PC would, or that they face greater or lesser risk, or stand to have more or less impact. Following the action procedure is crucial: traits, gear, and the fictional situation are what determine whether an action roll has to happen and what the outcomes mean.

Action Rolls

If a PC’s action is risky and there is something at stake, roll your Vigor die and your Momentum die, then add them together:¹

• 6 or Lower - Consequence. You face the consequence you risked. This might mean you fail to make an impact, but it doesn’t have to. Step down your Momentum die.
• 7-9 - Mixed. You mostly do what you set out to do, but with an additional complication or cost. You may suffer a partial consequence, have lesser impact, or have to pay an additional cost.
• 10 or Higher - Success. You accomplish your intent without unforeseen complications or costs. Step up your Momentum die.
• 16 or Higher with d12 Momentum - Wild Success. You accomplish more than you had hoped for, but you also cause trouble, suffering a serious backlash and reducing your Momentum die to d4.

NPCs do not make action rolls. The Ref states what they do and determines the outcome based on the fiction. A PC can act to prevent an NPC’s action, which may require an action roll.

Managing Momentum

High Momentum is powerful, but it can also be risky. Sometimes it’s best to voluntarily lower it to lessen the risk.

• Take a Breather. Take a few moments to catch your breath and calm down to step down your Momentum die by 1 size.
• Showstopper. If your Momentum is d12, you can cash it in to automatically score a Success on an action roll, then step down your Momentum die to d6.

NPCs

NPCs have different attributes from PCs: Danger and Endurance.

• Danger. Danger indicates how severe the consequences might be if a PC fails an action roll involving this NPC, measured on a scale from 1 to 3. Environments and non-NPC threats also have a Danger score.
• Endurance. When an NPC suffers harm, reduce their Endurance by the amount of damage taken. At 0 Endurance, an NPC is taken out. Depending on the type of harm, they might die or simply be too injured or fatigued to act.

If a dangerous situation looks bad for an NPC, like if their allies fall or they’re seriously injured, they test their Morale. The Ref rolls a d8. If the result is equal to or under the NPC’s current Endurance, they hold firm. If the result is over their current Endurance, they retreat or surrender. Danger 3 NPCs roll twice and take the higher result for Morale tests.

Harm & Wounds

When you get hurt or suffer fatigue as a consequence, you take damage. Step down your Vigor die a number of sizes equal to the damage taken. The damage something deals is usually determined by its Danger.

If your Vigor steps down below d4, suffer a Wound. Mark one of your traits: it is no longer usable until your Wound is healed. Work with the Ref to describe your Wound, which doesn’t have to be physical. The Wound’s Severity is equal to the Danger score of whatever caused the Wound. The Severity determines how long it takes to heal and how likely it is to cause a Scar (see Recovery & Repair).

Then, your Vigor die rebounds to its current maximum. Your maximum Vigor is reduced by Wounds: with 1 Wound, you have a max of d6, and with 2, a max of d4. Your third Wound is fatal.

Avoiding Harm

• Armor. If your gear provides you Armor, you can mark 1 Armor to absorb 1 damage from a source that Armor can prevent. Repair Armor using Supplies during a rest to unmark.
• Lucky Break. You can choose to step down your Momentum die by 2 sizes to reduce the damage you take by 1. For example, if you have d4 Vigor and d10 Momentum and you take 1 damage, you can reduce your Momentum to d6 to avoid a Wound.

Pathos

If your Momentum steps down below d4, it rebounds to d6 and you suffer Pathos, an unhelpful inversion or intensification of your Drive. While suffering Pathos, your Momentum can’t go above d6.

Pathos clears when you complete a mission, or when you do something inconvenient or problematic to get it out of your system. To reiterate: to relieve Pathos during a mission, you must let it cause a real problem, subject to the Ref’s discretion.² If your Momentum steps down below d4 while you’re already suffering Pathos, take 1 damage instead.

Pushing Yourself

If you’re not suffering Pathos, you can push yourself to treat your Momentum die as a d12 for a single action roll at a time. However, this is risky: if you fail the roll, step down your Vigor die in addition to any other consequence you face.

• When you step your Momentum die up or down after this roll, use its actual value, not the temporary d12. For example, if you push yourself while you have d6 Momentum and succeed, your Momentum steps up to d8.

Consequences

There are any number of potential consequences for a PC's risky action. When it's not obvious from the fiction, pick something from the list below. If nothing fits, maybe the action's not so risky after all.

• Harm. A threats deals damage equal to its Danger. If the harm comes with another effect, decrease the damage accordingly.
• Cost. Use up more of a resource than planned.
• Lost Gear. Temporarily lose a piece of gear or a resource. The PC has to go out of their way if they want it back.
• Damaged Gear. Damaged gear is less effective and at risk of breaking if used again. Danger 3 threats can outright break gear.
• Spend Time. The Ref makes an event roll³ or two.
• Complication. Another threat or obstacle arises, possibly hindering another PC.
• Social Problems. Lose standing with an NPC, faction, or community, make a new enemy, or damage your relationship with a friend.

Gear

By default, you have 6 slots for gear, which includes weapons, armor, useful tools, and Supplies.

• Weapons. Weapons deal damage equal to the number of slots they occupy, and require that many hands to wield. Rare 3-slot weapons still take two hands, but require you to remain stationary while wielding them.
• Armor. Armor can absorb damage equal to the number of slots it occupies before it breaks.
• Durability. Each piece of gear can be damaged. Damaged gear is less effective and is at risk of breaking completely if it’s damaged again. You can repair gear with Supplies during a rest (see Recovery & Repair).

Recovery & Repair

Resting in a safe location restores your Vigor to its current maximum and resets your Momentum to d6. You can also use Supplies to repair one piece of gear per rest. Each time you rest, the referee makes an Event Roll as time passes.

• Healing Wounds. Wounds heal between missions, at a rate of 1 Severity healed per mission completed. That means any 1-Severity Wounds heal after the mission they're gained in. 2- or 3-Severity Wounds linger for multiple missions before they fully heal. Healed Wounds might leave Scars (see Growth & Change).

Growth & Change

• Experiences. At the end of each mission, each player can identify an important experience their PC had during the mission to potentially inform a new trait. If they have fewer than 5 total traits, they can add the new trait to the list, working with the Ref on the wording. If they have 5 or more traits, they roll a d8 and add a new trait if they roll above their current number. If they roll equal or lower, they can either replace a trait with the new one, or forgo gaining a trait.⁴
• Scars. When one of a PC’s Wounds heals, the player rolls a d6. If they roll equal to or under the Wound’s Severity, they gain a Scar: modify or replace the trait that was marked to reflect how the Wound has changed it, working with the Ref on the wording. If they roll above the Wound’s Severity, the Wound heals cleanly and the trait works as normal.

Unanswered Questions

While I'm (unfortunately sporadically) testing this system, I'm trying to figure out the answers to a few questions. Or these might be problems seeking a solution. Let's find out.

Is the Action Procedure Too Slow?

A nice thing about numerical stats is that, well, they're quick to resolve. Roll under a value. Roll and add a value. Roll that many dice. Maybe you have to discuss which stat or skill applies, but how it applies is simple.

Here, not so much. Here, if a PC has a trait or gear that could help with something, the player and Ref have to discuss how, and what that means for the potential roll and its results. At first, that can be slow going, but maybe with a few sessions under a given table's belt, it'll require less and less conscious deliberation. Maybe it'll start to feel more natural. Unfortunately, I haven't had time to test this enough to see if that's the case yet.

Is Momentum Too Powerful?

I've been going back and forth on how exactly Momentum steps up and down. Is it too easy to step it up? Once it's there, is it too easy to keep it there? The goal of the "Wild Success" is to prevent it from being too powerful a snowball effect. I'm curious to see how that bears out with more testing.

Character Creation

Right now, PCs start with an Origin (their home world, which also gives them their species), a Role on the crew, and some sort of Prior Experience that gives a PC their first Experience. I'm still working on tables for these, though I do have the Origins:

• Mercurian. Gullfolk from a hot, humid ocean world. You don’t need aether-wings to maneuver in open aether, but can only glide in less dense atmospheres.
• Eosi. From the twin worlds that comprise Venus, the stars Phosphoros and Hesperos. You have two distinct appearances you can switch between when you rest.
• Gaian. Earthlings are known for hardiness and endurance. You have +1 inventory slot.
• Jovian. From dangerous, ever-changing Jupiter. You look like an organic machine of wood and vine, but are born, not built. When you rest, you can modify your body: choose between an extra limb, 1 innate Armor, or enhancing one of your senses.

The intent is that words like Gaian or Jovian function as traits, giving you an edge on actions that relate to your home world or species, and you also get a little special feature. The PC's Role, like the Face, Recon, Medic, or the Heavy gives them another trait and their starting gear. Finally, their Prior Experience gives them a bit of backstory and an Experience trait.

PCs also get a Drive, representing their motivation. Still working on how Drives integrate mechanically, if at all. The Drive also determines a PC's Pathos: it's an unhelpful intensification or inversion of their Drive. Think something like Curiosity as a Drive and Obsession as the Pathos version, or a Drive for Greatness that turns to Arrogance under duress.