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Operation Unfathomable
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Operation Unfathomable

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BEHOLD the Underworld in all its bewildering majesty as titanic Chaos Godlings and their unsavory cults make genocidal war upon each other!

SEIZE eldritch artifacts and treasures far above your lowly station!

THRILL as you throw the gauntlet of your life into the smug face of the unknowable and embark upon OPERATION UNFATHOMABLE!

OPERATION UNFATHOMABLE is a 108-page, internally-consistent, gonzo funhouse module for Swords & Wizardry that runs like a subterranean wilderness trek instead of a “down the 10 foot hall and kick in a door” affair. There are random elements aplenty to keep GMs guessing as well as players. No balanced encounters to be found here, but the clever setup allows low level characters to drop into the dungeon “deep end” and still have a chance of making it out alive—if they’re smart and wary.


  • Underworld Phenomena: Novel environmental hazards to challenge explorers like Horizontal Cave Lightning, Whirlwinds of Unbidden Transportation, Sudden Seismic Events, and many more! 
  • Fractious Factions: Enter a crossroads of Underworld civilization where combat is only one of the options (and often not always the wisest!) for dealing with its denizens. The PCs can make a temporary truce with Blind Antler Men or forge an unlikely alliance with the minions of Nul the Mindless God! 
  • Races, Weirdos and Chaos Godlings Galore: Over two dozen new creatures, from Batwinged Dwarfs to Shaggath Ka the Worm Sultan, malevolent...and even more malevolent!
  • Near-Endless Adventure: Enough NPCs, encounters, and areas to explore to keep a campaign going well beyond the initial scenario.

From the author: "I wrote OPERATION UNFATHOMABLE originally to be a one-off adventure and for utility as a convention scenario. As such, the gloves were off both in terms of danger level for player characters and the campaign-changing potency of the enchanted treasures they might run off with. Going against my own advice, I used it to start a campaign.

Four years and hundreds of game-hours later, the campaign continues (and is still fun). As every DM knows, there is no substitute for play when it comes to breathing life into a setting. I believe the Underworld of OPERATION UNFATHOMABLE has that lived-in feel precisely because it has been explored extensively at the table and its secrets probed by a number of minds sharper than my own (I have awesome players).

I hope you enjoy it as much as I have."

 - Jason Sholtis  

"Gonzo, fanciful, hyper-realistic, it is one of the most imaginative, and fun, things you will ever run...There’s little to no game balance present, it’s the brave little tailors vs The Strange. At heart, a pretty straightforward cave crawl looking for the pretext item, it shouts Come At Me Bro, at every turn, daring the party, over and over again, to engage. Enticing them. Luring them. Magnificent." -- Bryce Lynch

"Operation Unfathomable is perhaps the first OSR "dungeon" I've seen (with the possible exception of Michael Curtis's Stonehell) that truly mines the "mythic underworld" concept for all its worth. Imagine Richard Sharpe Shaver's Lemurian ravings as drawn by Jack Kirby in the throes of a fever dream and you're on your way to getting a small sense of what Sholtis presents here...By almost any measure, Operation Unfathomable is a triumph, an extremely imaginative adventure and setting, attractively presented and chock full of reckless old school dungeon delving fun. I cannot recommend it highly enough." -- James Maliszewski

DOWNLOAD THE 11"x17" DM's MAP, Player's Map, and Character Sheet here


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Reviews (2)
Discussions (10)
Customer avatar
Gus L June 22, 2018 7:03 pm UTC
While I can't review this here because I got it via kickstarter - Operation Unfathomable is a wonderful product very much in line with the gonzo science-fantasy strain in DIY products. It would fit almost seamlessly with Anomalous Subsurface Environment and vice-versa. It's a large well-organized underworld crawl, fun, challenging and ripe for expansion into a campaign.
Customer avatar
Jacob C June 06, 2018 7:13 pm UTC
Does anyone have an issue with POD version displaying completely degraded image quality (washed out blacks and weird fuzzy pixelation) on the artwork? The PDF looks 10x better compared to my print copy. Is this just to be expected with the provided quality option?
Customer avatar
Kurt M March 02, 2018 11:11 am UTC
Okay. A matter of some speculation and no little debate: How do you pronounce the Prince's name? In our discussions, several versions were suggested. "Aye-Ray-en" was quite popular. "Ih-rain" has id proponents, as does "Aye-rain"--but me, difficult and pernicious fellow that I can be, I liked an altogether different pronunciation, one that changes the tone of some exchanges significantly. The vowel combination "ae" coming out of the Greek, was used to denote a long E sound. "Aegypt" is pronounced "E-gypt". "Daemon" is NOT "day-mon" but just an alternate spelling of dE-mon". So, Iyraen could be pronounced, hee hee, "Aye-reen". Which I find endlessly amusing for some reason.
Only the pronouncements of Those Who Know can end this debate. With, um, pronouncement. er, I mean, pronunciation. of that Prince guy's name...y'know.
Customer avatar
jason S March 03, 2018 1:21 pm UTC
Official word from Hydra Co-op's Minister of Pedantry: Let the unfortunate prince's name be pronounced "Aye-reen".*

*unless you don't want to
Customer avatar
Kurt M March 05, 2018 11:18 am UTC
You heard the Man, boys! Let's go find Aye-reen and get the King's rod back.
quit snickering Gorgamus, I swear, you're first down the ladder if you don't shape up!
Customer avatar
Shane M February 16, 2018 10:23 pm UTC
How many hours of gameplay do you reckon this is good for? Wondering if it would work for a one-shot
Customer avatar
jason S February 17, 2018 12:16 am UTC
It was originally written as a convention scenario, to be played in 4 hours. It can still be used as such as I have done on several occasions, one of which happened to lead to a five-years-long campaign. To reach a satisfactory conclusion using this expanded edition the players must refuse to be tempted by off-mission opportunities for self-enrichment or exploration which could chew up many hours. I think you'll find it fun even if they don't.
Customer avatar
Shane M February 17, 2018 5:09 am UTC
Thanks! Sold!
Customer avatar
Andrew W February 12, 2018 1:43 pm UTC
Is this exclusively for low-level adventuring parties or is there any mid-to-high stuff in there?
Customer avatar
jason S February 12, 2018 4:33 pm UTC
There is plenty of mid-to-high level stuff in there. The hook for the initial scenario is that a low-level party could slither in and possibly survive due to a recent incursion by a high level NPC party leaving a path of dead monsters in their wake, but a mid-to-high level group would find all kinds of challenges suited to (and at times exceeding) their level of expertise.
Customer avatar
Noah G February 09, 2018 11:35 pm UTC
Which systems' stats are in the Appendix F? Thanks!
Customer avatar
jason S February 10, 2018 5:02 am UTC
Swords & Wizardry Core
Customer avatar
Noah G February 17, 2018 1:29 am UTC
Nice! OK I'm onboard - buying now :-)
Customer avatar
Chris C February 08, 2018 11:54 pm UTC
Can't decide whether to get the pdf or wait for the paper version...
Customer avatar
Lee W February 09, 2018 5:26 am UTC
Me either. I wonder if we buy the pdf now, if we’d get credit towards a potential pdf/print bundle. I also wonder how long the POD will take.

Didn’t know about the KS. Otherwise I would have backed.
Customer avatar
Paul W February 08, 2018 4:57 am UTC
I'm a super-biased reviewer (and can't review it directly, I guess because I got it through the Kickstarter), having played in Jason's OU game for years and helped out with the upcoming DCC version of this book, BUT -- if you don't get this, you are seriously missing out on Jason's amazing talent, both as a writer and artist. For me, it has been the best experience in a D&D-esque game in my lifetime, and I've played for 30 years. The book is Friggin' Beautifully laid out and the PDF is the most functional I've seen.

So, yes I'm 100% biased, but I can objectively say you'll be sad in your life without this book on your shelf and gaming table.
Customer avatar
Michael N February 06, 2018 6:02 pm UTC
Will there be a POD option?
Customer avatar
Humza K February 06, 2018 9:28 pm UTC
Yup - working on getting the proofs.
Customer avatar
Michael N February 07, 2018 4:08 am UTC
Nice! It looks nuts, but in a good way
Customer avatar
Jason K February 22, 2018 7:37 pm UTC
Proof faster. Print now. Waaaaaaant!

Seriously, the pdf is awesome but I want the genuine artifact at my table. This is so good. Oh, and when will the DCC conversion be ready?
Customer avatar
jason S February 22, 2018 10:46 pm UTC

We had some issues with our original proof (though it looked pretty sweet otherwise), so the process continues for now....soon!
A no-frills DCC conversion doc is in the last stages of editing.

Customer avatar
Jason K February 23, 2018 12:12 am UTC
Excellent. I’ll try to improve my patience in waiting... it’s good stuff man.
Customer avatar
Jason K May 07, 2018 12:50 pm UTC
James Raggi just uploaded a photo of OU in a dead tree format... does this mean it will soon be available in print?

Also, how’s that DCC conversion coming?
Customer avatar
Todor P February 06, 2018 12:01 pm UTC
With all due respect, a $12 product should have at least a single interior spread to give some idea of the art and layout. Otherwise, it's just a huge no-go, even with the full table of contents.
Customer avatar
Gordon C February 06, 2018 2:23 pm UTC
As someone who has already gotten their hands on Operation Unfathomable through the Kickstarter, it would be a mistake to pass this up.
Customer avatar
Humza K February 06, 2018 9:27 pm UTC
Thanks for the feedback! We've edited the full preview to let folks get a glimpse of the interior.
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This title was added to our catalog on February 05, 2018.