Barsoom brainstorm


The Conan OGL varient seems like the perfect chassis onto which to bolt a Barsoom setting. John Carter's martian adventures are by far my fave of ERB's series, and my favorite of the "martian adventure" stories.

It strikes me as a really excelent RPG setting in the d20/OGL mode. In no particular order, some riffy ideas:

Like in Conan, races get bonus skills, ability bonuses, special abilities, and favored & restricted classes.


(and offworld)




A set of telepathic skills & feats. The mentalist gets bouns telepahtic feats and has all the telepathic skills as class skills. Latent telepahty seems like a normal and common thing on Barsoom, but some would develope it as a specialized art or science. Psychic powers on Barsoom are mostly 'soft' (no TK style effects) with mesmerism & telepahty being common. Some minor 'kinetic' powers available to dedicated Mentalists might be in order.


Since no one wears armor, the bouns for Dodge/Parry needs to be upgunned a step for each class & there needs to be lots of dodge/evasion special abilities and feats... otherwise it's death for all, especially with radium firing guns. Gun-related feats (Two-gun fighting, sharpshooter, fastdraw etc.)


Codes of honor unique to Mars (A Greenman of honor will respond only in kind when attacked- if attacked with fist, he must respond with fist etc.)

Technology of mars (flying ships, radium guns, advanced medicine etc).

High Adventure- the 'flavor' of ERB's Mars... what it is to adventure there, and which metagame considerations need be accounted for with mechanics?

A good resource for any such conversion:




Already doing it, in an online game ;)

I'm using the D20 Moden Rules for character creation, but I am using the Conan rules for combat.

Since Conan hadn't hit the shelves when I started the planning of the game, I'm simply having PCs of differing races pick feats that best represent their race. Want to play a firstborn? Pick feats that represent physical perfection. Want to play an Okarian? Take "Exotic Weapon - Hooksword".

The excpetion is Tharks, for which I simply use the Centaur stats. (although this has meant having all PCs start at L6)

I wouldn't recommend having Earthman PCs tho, as they would simply be *way* to powerful.

But yes, I agree that the Conan rules, in general, are almost perfect for a Barsoom based game, if you were to create the races and classes that suited. I think you would want to consider the Red men as seperate races, too - a man of Mantor is liable to have wildly different skills that a man of Helium

Not sure any race qualifies as Barbarian, tho. Even the Green Hordes have very high-tech skills. If anything, they are closer to nomads.


For Radium weapons, I used the D20 Modern S&W M29 .44 Magnum revolver, and the Barret Light-Fifty Sniper Rifle (with built in electro-optical scope and range incrememtn increased to 150), but ruled that they did 1 extra die of damage when used in natural light due to the explosive ammo (So, totals of 3D8 and 3D12, respectively, and the extra 1 Dice of damage done by the extra dice is applied to anyone in the same square as the victim, too)


Also, check out Sean K Reynold's D20 Barsoom Bestiary.


Playing an Earthman on barsoom is part of the fun of the setting... the outsider experiencing the setting for the first time. It makes a great way of dropping a player into the game who has no idea about the setting.

As for power... I'd say thety arn't all that over the top. They have a native mind shield, but can't learn the higher disciplines of telepahty (can't take the Mentalist class), they can leap due to their Earth-honed muscles, but this isn't any kind of overwhelming advantage. Further, they are going to start with no proficiency with Barsoomian weapons, technology, or culture... a prety major disadvantage and limit on starting skill choices. Mechanically, I think allowing Earthmen to jump (and fall) a distance equal to their Jump skill check x 5 feet would cover this super-leaping. An ability modifier I would apply would be a +2 to Strength ballanced with a -2 to Dexterity.

The Greenmen/Tharks look impressive... but Carter as much as says that they arn't much stronger than a well-built human. They ballance just fine with the other races in my mind... large creatures obviously. He also kills two of them- great warriors at that- with his barehands. One with a single punch. Clearly no where near as tough as a Centaur (and clearly, Carter was packing Improved Unarmed Strike & Brawling with perhaps a Fate point backing the punch).

I'd set up the Red men like Hyboreans in Conan- they pick their bonus skills to reflect their upbringing. This would make the Redmen the most versitle of the races (and as they are the dominate humanoids on Mars, this seems fine).

Seriously- I see all the races (even Tharks and Earthmen) as pretty well ballanced.



Bailywolf said:
Playing an Earthman on barsoom is part of the fun of the setting... the outsider experiencing the setting for the first time. It makes a great way of dropping a playing into the game who has no idea about the setting.

As for power... I'd say thety arn't all that over the top.....[snip]....An ability modifier I would apply would be a +2 to Strength ballanced with a -2 to Dexterity.

There is the difference, then - the bonuses you consider appropriate to Earthmen are *paltry* compared to what John Carter and Ulyses Paxton display in Mars' low gravity. And the reduction in dex makes no sense at all - many, many times Carter refers to the superior dexterity his earthly muscles give him.

You may see Carters 1-punch kills as a sign of Green Man weakness - I see them as a sign of Carter's strength.

However, this isn't really an appropriate conversation for the Conan forum. There is a Barsoom thread in the "What should Mongoose Publish Next" forum, if you want to continue the discussion.


The implication, in my opinion, was not that he killed them in one punch because he was an especially skilled fighter but that his muscled exerted so much more power on Mars that he could kill with a single punch. I think that's why Mayhem thinks they are too powerful.

My solution would be, and I don't really plan on doing this, to have some reasonable amounts of special abilities for Earthmen -- you mentioned mindshield, leaping ability, tempered by no Mentalist class. Then I would apply +2 Str, +2 Dex, -2 Cha (or +4 Str, -2 Cha). It shows how John Carter was a superb physical specimen on Mars (not just strength, but his agility seemed improved) but also reflects that his skin made him an oddity which could lead to resentment of his abilities, distrust and dislike. It's not perfect, of course, because John Carter went on to become very popular, not just with the ladies :D but also with many others.

Edit: Also, I agree with Mayhem that Carter probably was more like +4 Str, +4 Dex on Mars (or maybe more!) but for RPG purposes and some semblance of balance, I think if you are going to have Earthmen in your Barsoom, then tempering it makes sense.


I checked out the other thread- not exactly on topic.

And there is a perfectly workable Lankhmar conversion thread going here... and considering I want to use Conan to play Barsoom, this is the place to rap about it.

Anyhow... You have to figure Carter hits Mars as something like a 10th level Soldier/Scout (minimum) with some heroic ability scores to start.

A 1st level Earthman is going to be ballanced quite well aganist other 1st level native characters.

I would also er on the side of oportinity... denying a player the option to play an Earthman sorta sucks.

Conan is just this side of superhuman in many of Howard's stories, but he maps quite well into the RPG system. I think you can do the same with John Carter on Mars if you assume he "begins play" as an experienced character with heroic ability scores.

I suggested the Dex penalty because Carter spends weeks creeping around trying to get his feet in Martian gravity... in terms of raw speed, he was superior to a native martian, but in terms of fine dexterity...

Ah well, it's one of those squishy areas you get when you try and adapt the inconsistancies of serialized adventure fiction to the kind of nuts-and-bolts needed to make a game system.

I would make every effort to get the 'flavor' of ERB's Barsoom without going for such a literal interpretation of everything...

I'll monkey with basic mods and post them as as plug-in modules just for giggles.




Like John Carter, a few Men of Earth find their way to the red planet. Upon Barsoom they find their Earth-born muscles vastly more powerful when confronted with the lesser gravitation and atmospheric pressure. This raw physical superiority is essential though, for without it no stranger to the ways and traditions of Barsoom could long survive there. An Earthman could live upon Barsoom for a lifetime, and still not entirely understand the weird and ancient ways of its native peoples.

The well-developed emotions of an Earthman can be unseemly to many Martians, but they serve an Earthman well when the application of some basic kindness proves more effective in dealing with the lower creatures than the most sound thrashing. An Earthman’s feelings are rarely hidden to Martian eyes, but his thoughts are effectively cloaked from the innate Martian telepathic senses. An Earthman can learn to project his own thoughts well enough to be understood in the Martian language, or to make his wishes known to domestic beasts, but the higher telepathic sciences are impossible for an Earthman to develop.

Ability Modifiers: Earthmen gain a +2 to their Strength

Favored Class: Pick one to represent the Earthman’s life before coming to Barsoom. After, this is his favored class.

Prohibited Class: Mentalist. An Earthman my never learn the higher mental sciences.

Lifting and Springing: An Earthman’s muscles and bones have evolved to the strength of Earth’s gravity and atmospheric pressures. Upon Barsoom, these powerful muscles work against much less resistance. An Earthman’s jumping is not limited by his own height, and further all jumping distances are multiplied by 3. An earthman can lift and carry three times what his Strength score would normally allow in the Martian gravitation.

Mind Shield: All Earthmen have the Mind Shield feat for free, but unlike native Martians, they can’t willingly lower their shield in order to allow telepathic reading. Further, they can’t select any other Telepathic feats other than Improved Mind Shield and Greater Mind Shield.

Bonus Skills: Bluff; Handle Animal; Jump; Ride; Tumble

Mark of Strangeness: Earthmen are easily recognized as outsiders by all natives of Barsoom. Their telepathic speech is easily recognized for its alien character, and their appearance differs from the native races in several ways. Further, the myriad customs and cultures of Barsoom are nigh impossible for the non-native to master. Earthmen suffer a -2 penalty to the following skills if the GM rules this Mark of Strangeness interferes in their normal use: Appraise; Craft (Barsoomian Technology); Diplomacy; Disguise; Gather Information; Knowledge (any local or cultural); Sense Motive.

Weapon Proficiencies: Due tot heir unfamiliarity with Barsoomian technology and weapons, the following weapons are always exotic for Earthmen: Radium Firearms, 40’ Lance, Concave Buckler, and Hook Sword.