The New OSR 4: Blades of Barsoom

I’ve been posting a bit recently on the “Cepheus Engine as the New OSR” notion I’ve been playing around with. The idea is that the Cepheus Engine (basically old-school Traveller) should be a lot better known, and would make an excellent core for a OSR-style community of players and developers.

My Cepheus as a New OSR posts:

First, I explained a bit about the Cepheus Engine, and why it’d work as a new OSR community.

Second, I explored the various versions of Cepheus, and how they might be used as the base for new games.

Third, I listed a collection of resources for designing Cepheus settings.

For this post, I’ve decided to put put my money where my mouth is, and actually use the tools I’ve posted about above to design a setting.

The Basic Idea – Blades of Barsoom

Barsoom. The dying Mars setting of Edgar Rice Burroughs’ John Carter series of novels.

Even if you’ve never read the books (you should, they’re fun), you know all the tropes: A lone Earthman trapped on an alien world, exotic races on a dying planet, and a beautiful princess to rescue. Burroughs certainly didn’t invent these ideas, but he packages them beautifully, and one can still trace their influence through the maze of popular culture to the present day.

Burroughs’ Mars is a wonderful adventure setting – swordplay, derring-do, and monsters galore. It was a big influence on early D&D, and there have been multiple Barsoom-set roleplaying games in the last few decades. I’ve compiled a list of them here.

My idea is to make my own Mars adventure game using the Cepheus Engine. My working title is Blades of Barsoom. Conveniently, the first few John Carter books are all in the public domain, so I’m free to use them for source material. The prolific Michael Brown put out a Cepheus setting called Blades of Tyri that covers similar Sword & Planet ground, but I’d like to see something more explicitly Barsoomian.

Mockup of a cover for Blades of Barsoom. The image is from Midjourney, but if I actually finish this, I’ll hire a real human artist.

Note that all of this is very much a work-in-progress.

Which Cepheus?

As I covered in my second post, there are multiple versions of Cepheus one could use as the basis for a game. First, I’ll have to decide which one I want to use.

Quantum Engine Logo

Barsoom is a high romance, high adventure sort of world. I’m thinking the heavy rules of the SRD are a bit much. I’m also thinking the complex, lifepath character generation in the SRD and Deluxe is a little too detailed for this setting. Barsoomian characters don’t really have deep backgrounds; they’re pulp archetypes who spring into existence ready for action.

Also, a list of skills also seems a little unnecessary. People on Barsoom mostly seem to either have knowledge, or the ability to fight – not much else.

So that leaves me with the Quantum Engine, the light SRD from Stellagama Publishing.

What Stats?

The base version of the Quantum Engine has 6 stats – Combat, Technical, Knowledge, Physical, Social, and Stealth. Other games, using the Quantum Engine as their core, add stats like Sorcery or Survival. I considered adding Survival or possibly Pilot (for Barsoomian airships), but for now I want to keep it simple, so I’ll just use the core six.

Character creation will probably be as follows

  • 2D6 for Endurance
  • 4D6 for Lifeblood
  • Choose one Trait
  • The character will get 6 points to distribute amongst the skills. In Quantum, it’s normally 5, but I wanted Blades of Barsoom characters to be a little larger-than-life.

I’ll probably give each character 3 individual Hero Points to start out with

Races of Mars

Burroughs’ Mars has all manner of intelligent races. Here’s my initial thoughts on how they’d be handled:

Human, Green Martian, Red Martian

Red Martian: This will be the default species of the setting. No special abilities.

Green Martian: The towering green barabrians of Barsoom start out with a free point in Physical, but canot have any points in Technical. They’ll also have the Four-Handed trait. When in social settings outside Green Martian tribes, they have a DM-2 to all Social rolls.

Human (Jarsoomian) – Will have the Jarsoomian Leap trait. As they’re aliens on Barsoom, humans cannot start out with a Knowledge skill.


Here’s some initial Barsoom-specific traits. I’ll certainly be adding more.

Jarsoomian Leap: Raised in the stronger gravity of the 3rd planet, you can leap enormous distances with ease.

Speaker to Banths: You have the ability to soothe and befriend (though not tame) the Banths, the wild lions of Barsoom. They will not attack you and will defend you if you are attacked.

Four-Handed: You have four arms, and can make a second action in a round. A second attack will be at DM-2.

Based on what I have so far, I have enough to mock up a simple character sheet:

Blades of Barsoom Character sheet
I forgot to add Four-Armed to this sheet.


For most combats, the basic Quantum rules should be fine. However, I’d like to have something a little more swashbuckler-style for some of the melee fights. I’m thinking of adapting the Swashbuckler rules Peter Kreft detailed in the Cepheus Journal #6 (free to download).

In Peter’s system, each combatant gets a number of Action Points (AP). During a round these can be spent on various offensive and defensive actions. It’s designed to make combat a little more detailed and flavorful. You can spend all your Action Points to attack, or save them to defend.

The original system was designed for regular Cepheus, so I’ll have to modify it a bit for Quantum.

Characters will have a default of 3 AP. They can add their Combat stat to that total.

Here’s the combat actions that I’ll probably use. I’ll almost certainly add others.

Attack: AP Cost: 2, Normal Attack – Combat 8+
Dodge: AP Cost 1, Avoid Blow – Combat 10+
Parry: AP Cost 1, Block with Weapon – Combat 10+
Disarm: AP Cost 1, Knock weapon from opponents hand – Combat 12+
Recover Weapon: AP Cost 2, Recover weapon from ground
Block: AP Cost 1, Block attack with other object – Combat 12+

I’ll probably also use the Heroes & Grunts rule from Cepheus. It seems appropriate for the pulpy setting.

Scenery Rules

In swashbuckling movies, characters always are using the scenery in dramatic fashion – swinging on ropes, cutting chandelier ropes to pull themselves into the rafters, using a blade to descend down a tapestry, etc.

I’d like to account for stuff like that mechanically in my game, to encourage that sort of dramatic action movie nonsense.

My initial idea (sort of stolen from Cavaliers of Mars) is that each location would have a number of bits of scenery, each with a Scenery Points (SP) value. If a player interacts with them to do something, usually to travel quickly, they can make a roll (usually Physical) to do something and add the SP value.

Alternately, the SP value could be used in combat, i.e. adding SP to a Combat roll by dropping a chandelier on the heads of the Jeddak’s guards

Example location – Jeddak’s Palace

Chandelier: 2 SP, cutting rope can bring one person to upper level. Can only be used once.
Water slide to Fountain: 1 SP, from upper balcony to floor.
Heavy Tapestries: 2 SP, can block entrance if cut.

I’m still tinkering with this idea, and haven’t tested it yet, but I think there’s a flicker of a good idea here.

Airship Combat

The Martians travel across the wastes of Barsoom in their amazing flying ships. The city states of Barsoom all have mighty fleets of airships to make war on one another.

The basic vehicle combat rules in Quantum should work fine for this. All I’ll need to do is make modified vehicle damage tables and stat up some Martian airships.

Martian airships
From the somewhat underrated (but not by much) 2012 John Carter movie


Barsoom is a dry world, so I’ll probably have some simple desert survival rules, probably adapted from the Traveller supplement The Desert Environment from Gamelords.

I’ll also throw together a bestiary of all the exotic creatures that Burroughs described.

The lists of equipment shouldn’t be dramatically different from the Cepheus books, with the exception of the rifles.

Martians use fairly powerful radium rifles in the books, with 100 round magazines and 200-mile ranges. I’ll probably weaken them considerably, in order to encourage more swordplay over gunplay.

In the books, armor isn’t really worn. Technically all of the Martians are nearly naked. I may have some sort of Endurance penalty for wearing armor in the Martian heat, or just make it impossible to find armor in the setting.

There’s also some dueling rules in Zozer Games’ Godstar that I may steal as well.


Obviously, it’s far from finished, and the success of a setting depends more on the presentation than the base rules, but I think I’m off to a decent start on this.

I’m going to continue tinkering with this, perhaps get some playtesters, and will post some more excerpts when they’re ready.

2 thoughts on “The New OSR 4: Blades of Barsoom

  1. Fantastic start! I’ve been closely following this series of New OSR posts and agree that CT/CE/QE are ripe for DIY games. And with all the self-publishing tools available easy to print up nice copies for the table, as I’ve done recently with Lulu.


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