Gary Gygax' Greyhawk / Barsoom Crossover adventure on Mars?

“As you know I am not of Barsoom; your ways are not my ways, and I can only act in the future as I have in the past, in accordance with the dictates of my conscience and guided by the standards of mine own people.” All RPGs base based on Edgar Rice Burroughs' Barsoom stories can be discussed here.
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Gary Gygax' Greyhawk / Barsoom Crossover adventure on Mars?

Post by Havard » Tue Sep 11, 2018 4:03 pm

This quote is taken from one of the three Dungeons and Dragons (OD&D) booklets Underworld & Wilderness Adventures (1974) on Other Worlds:
Some areas of land could be gates into other worlds, dimensions, times, or whatever. Mars is given in these rules, but some other fantastic world or setting could be equally as possible. This function is up to the referee, and what he wishes to do with it is necessarily limited by his other campaign work. (p24)
This reference to Mars could easily be a way to promote TSR's Warriors of Mars which also came out in 1974. It could also be a reference to the time when Gary Gygax ran adventures for his Greyhawk group (LGTSA) which took them to Barsoom.

Gronan (Mike Mornard) talked about this adventure over at the OD&D forum:
@gronanofsimmerya wrote:
@archersix wrote:I'm really enjoying reading this thread.

I've read that Gary referenced Barsoom in his Greyhawk dungeon. Did you ever experience any Mars themed adventures? Did you see any other old science fiction references? Buck Rogers or Flash Gordon? Any Cthulu stuff? Or anything else?
I never went to Barsoom, but Ernie did, and Rob wanted to. There were some odd bits of science fiction (more "Sword And Planet," actually) in Greyhawk but it was a long time ago.

And there was a "Church of the Latter Day Great Old Ones," which we avoided like crazy.

Now, I guess the Oerth Solar System was later changed to adapt Greyspace to the Spelljammer setting, but could these stories and old references be used as background for a Greyhawk/Barsoom crossover adventure?


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Re: Gary Gygax' Greyhawk / Barsoom Crossover adventure on Mars?

Post by ripvanwormer » Tue Sep 11, 2018 9:53 pm

It was Erac's Cousin (Ernie Gygax's character) who traveled to Barsoom. There's more detail here: ... acs-cousin
One of Erac's Cousin's more memorable adventures occurred after he spotted a strange red star in the night sky. He drifted off to sleep thinking of the strange star and when he awoke he discovered he had been transported to Mars. To his surprise he arrived stark naked. Soon after his arrival, the mage was attacked by the Cannibals of Ugor. Much to his dismay, he discovered that magic didn’t work there, and he was forced to fight toe-to-toe with the bloodthirsty cannibals using nothing more than a tree branch. In time the unnamed adventurer adapted and ultimately excelled in is new environment. Due to the planet's low gravity the marooned wizard's strength was heroic. He could leap 20 to 40 feet into the air, and much further than that forward. During the many months that he spent there, being unable to use magic, Erac's Cousin began training as a fighter. Instead of using magic to defeat his enemies, he would now cut them down with a sword. Before returning to Oerth he had slaughtered hoards of Green Martians, and organized an escape from the mines of the Yellow Martians. Finally he discovered a method of returning to Greyhawk. He found Oerth in the night sky before going to sleep and when he awoke he was back home. Unfortunately his arrival home was similar to his arrival on Mars; naked. He had left a fortune behind on the red planet.
It's meant to be much the same as E.R. Burroughs' Barsoom so any resources for that setting would help flesh it out. Erac's Cousin reached the planet the same way that John Carter did, via astral projection after seeing it in the sky, though I think fan writers have put a portal leading there in Castle Greyhawk instead.

Barsoom is of course not mentioned in Spelljammer sources, but another planet in Greyspace, the gas giant Gnibile, is red in color and would appear as a red star in the sky. I've suggested elsewhere (in this thread, where I called it Torhoon after an alien race mentioned in Dungeon Magazine) that a Barsoom-like world could be one of Gnibile's moons.

Or if you don't mind interpreting the sources more loosely, maybe Erac's Cousin ended up on Athas.

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Re: Gary Gygax' Greyhawk / Barsoom Crossover adventure on Mars?

Post by grodog » Thu Sep 13, 2018 3:42 am

I would use TSR's _Warriors of Mars_ for Barsoom, and we had some extensive discussions/excerpts from it over on the old Pied Piper boards, and Marv preserved that info and a lot more useful Barsooming info/details on ODD74 @

re: Erac's Cousin's adventures in Barsoom, you'll want to read Gary's and Rob's accounts from their Soapbox articles from Dragon: ... apbox.html as well as Rob's account from Oerth Journal #5

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Re: Gary Gygax' Greyhawk / Barsoom Crossover adventure on Mars?

Post by Falconer » Fri Sep 14, 2018 5:28 am

Semi-OT, but I’ve sometimes thought about placing Tekumel as my D&D world’s “Mars” and whisking the D&D party there under a similar premise as Erac’s Cousin going to Barsoom. PCs in EPT are presumed to be “barbarians,” so, it’s practically built in!
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