The Substratum Protocol

The Substratum Protocol

When the anomaly appeared at the Earth's core, the Substratum Protocol was initiated. You are the best and brightest scientists we have left, our last hope to stem the apocalypse. You are the Substratum Expedition Team. Descend. Learn. Survive.
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A solo+ survival mystery TTRPG utilizing step-down dice and card draw mechanics, Substratum Protocol is playable as both a solo game or guided by a GM.
With players taking on the role of Earth's best remaining scientists, Substratum Protocol is our entry into the Deep Delving Mystery genre (like Subnautica and In Other Waters). 

On their grueling journey to the center of the Earth, members of the Substratum Expedition will overcome challenges, gain clues and knowledge of the anomaly, discover creatures, aliens, cosmic horrors, and ultimately assemble their final hypothesis to overcome the apocalypse looming before them. 


Descend. Learn. Survive. 

The scientists are well equipped with the latest in pressure suit technology

With over 90 pages crammed full of tables, creatures, mysteries, clues, and questions to answer, this will become your go-to game for impromptu sessions, short campaigns, or solo game nights.  

The game intertwines hard science fiction with the inescapable, unknowable horrors of an anomaly tearing apart reality.
  • Purpose-built for solo and multiplayer mysteries
  • Unique dice and card draw resolution mechanics
  • Take special Actions whose outcomes can chain together
  • Collect beaten cards during Skill Checks to power your suit's abilities
  • A self-contained story, with unlimited possibilities and outcomes
  • Quickly build unique and interesting characters at the table
  • 36 unique clues to discover, 36 questions to answer
  • 10 sectors to explore, each one stranger than the last
  • 120 events and encounters to surprise and stump your players
  • Build the Last Hypothesis: When they have learned all they can, the scientists must pour over their knowledge of the anomaly, construct the Last Hypothesis and enact their plan. Will it be enough?

Made by an All-Star Team of Creators

We've assembled a fantastic team to bring Substratum Protocol to life, including the group behind the wildly popular dwarves in space TTRPG, Stoneburner by Fari RPGs

  • Illustrations by Galen Pejeau
  • Editing by Eric Lazure
  • Developmental Editing by Ren√©-Pier Deshaies-G√©linas
  • Layout Direction from Tony Tran
  • Writing and Design by Andrew Boyd
  • Promotion by Alex from Backerkit

With twenty unique and interesting creatures to discover, the bestiary included in the Substratum Protocol is written as a field journal attempting to make sense of the strange new creatures. Discover creatures similar to ones we know - some you may want to keep as pets - but be prepared to grapple with creatures that eat the literal meaning of objects to sate their semiotic diet.

Sure, you're sold on the story, but you want to know what kind of dice you'll be rolling!

Based on the acclaimed Breathless system by Fari RPGs, Substratum Protocol uses a set of polyhedral dice and a deck of playing cards.

While making a scientist, players assign dice values to their Skills, from a four-sided die to a ten-sided die. 

When performing a risky action, players choose two Skills, then draw two cards. They roll the Skills’ dice and compare the sum to each card. If the sum is equal to or greater than the card, they beat it and collect it. The more cards you beat, the better the outcome.  

After a Skill Check, the highest rolled die steps down (example: a ten-sided die becomes an eight-sided die).

The collected cards can be spent in different ways to power your Exosuit's abilities, allowing you to heal, make new items, level up, and more.

Actually, here's a Free Preview PDF! (gdrive)

This preview includes the first 38 pages of the book! It includes all the rules and how to play, but does not include any of the information about the mystery, clues, knowledge questions, the sectors' events and descriptions, or the character folios.
Get the Free Preview! (gdrive link)

What is a tabletop roleplaying game without its character sheet? In Substratum Protocol, we have designed three unique bi-folded character sheets we call folios. All pledge levels come with print-friendly PDFs of all the folios.

Our physical folios are printed in full color on heavier, uncoated card stock paper that can stand up to the rigors of note-taking, erasing, and being tossed in your dice bag after the session.

Personnel Folio 

This folio contains everything players need, including a full rules reference for your Actions, die roles, and exosuit abilities. It allows you to track which clues and knowledge you have, your inventory, current Skill Dice ratings, and more. This is your main character sheet.

Team Folio

A dedicated character sheet for playing solo! When playing solo, you take on the role of the leader of the expedition and the other three members of your team share a single folio. The Team Folio, like the Personnel Folio, has a rules reference just for the solo player and managing their Team.

Mission Control Folio

Mission Control is the Game Master in Substratum Protocol, and because of the collaborative nature of the game, we have built a folio just for them to track the expedition's progress and members' stress, current depths and what pages the events are on for each, and a place to document the Final Hypothesis and the dice associated with the end game. And of course, a rules reference.


The Hints and Hijinx system that powers Substratum Protocol began its life as a purpose-built solo mystery TTRPGs system, with over twenty games made with it. This is why we call Substratum Protocol a "Solo+" game - we started with a solo system, and built it into a robust multiplayer game.

Substratum Protocol supports two styles of solo play - a more complex, free form method similar to playing multiplayer, and the original Hints and Hijinx format of solo play that is quicker to pick up and play through an expedition. Both are a ton of fun and give you room to explore and discover new mysteries on each play through.

One thing we love to do with our Hints and Hijinx games is making player artifacts - a dedicated themed journal for the game to document your entire journey in one place. All the members in your team, creatures you meet, dice rolls, adventures, clues, setbacks and successes of your expedition can be captured in a book to look back on or share.

Write, draw, color, add post-it notes, and clippings. Make the journal yours!

So we created the Expedition Journal. It has room to expand upon who you and your team members are. Document the clues, their location, and the context in which you find them. Track the questions the clues posed to you and your answers. And of course, there are plenty of pages to keep track of the events you encounter, and the rolls you made. At the top of each page you can key your entries back to clues, depth sectors, and events for quick referencing later.

At the end, you'll have an artifact wholly unique to you and your expedition.


Pick up the book and start your expedition!

  • Substratum Protocol book in hardback and PDF
  • Print-Friendly Character, Team, and Mission Control Folio PDF

Don't forget to pick up your Expedition Folio Pack for all the character sheets!


The Soloist's Toolkit includes everything you need to lead the expedition

  • Substratum Protocol in hardback and PDF
  • The Expedition Journal - a purpose-built journal to track your adventure, scientist, team members, clues, knowledge and your final hypothesis in print and PDF.
  • A printed Character Folio
  • A printed Team Folio¬†
  • Print-Friendly Character, Team, and Mission Control Folio PDF

 Get the PDF copy of Substratum Protocol

  • Substratum Protocol in PDF ¬†
  • Print-Friendly Character, Team, and Mission Control Folio PDF

Get Substratum Protocol, all its accessories, plus the entire Pandion catalog in Print and PDF. 

  • Substratum Protocol
    • Hardback Book
    • Soloist's Journal
    • 4x Character Folios
    • 4x GM Folios
    • 4x Team Leader Folio
    • All PDFs
  • Published Games and Journals
    • Badger + Coyote 2e
    • Dungeon Year Design Journal (condensed)
    • Hamsters & Himbos
    • Monsters & Counselors
    • Storyteller: A Campfire Narrative Game
    • The Tether Journal Bundle
    • The Cold Dark
    • The Jester King's Dance
    • Waffles for Esther
    • Whispers in the Walls 2e

Retailers only, please! If you have not purchased from us previously, please contact us with proof of your retailer status. Online and Physical retailers welcome. See the Pledge Tier for more information.
Customize your pledge with add-ons! Need more folios? Want to ensure you have enough Expedition Journals for multiple solo playthroughs? Don't forget to add them to your pledge!

All of our previously published works are also available as add-ons.


Substratum is a marvel of a game. The design of the book perfectly delivers the themes of danger and investigation. The game explodes with flavor and mystery as you delve deeper below the surface of the Earth, encountering strange landscapes and stranger creatures. The book is engineered to make the game accessible for both experienced and new players, and the innovative one-player mode allows for intense exploration with a team of scientists.
M. Allen Hall
Game Designer, Author

There’s plenty to love about Substratum Protocol, from the evocative setting to the fun mechanics to the amazing illustrations, but my favorite parts of the book are the phrases, anonymous annotations, and data entries with intriguing implications about the characters and their world. It's so good!
Dan Bronson-Lowe
Game Designer, Almost Bedtime Theater

When Pandion Games released the first version of the Substratum Protocol during the Breathless Jam of 2022, I was already a fan. The game was wonderful and innovative, yet still based around the foundations of the Breathless system. Almost two years later, Andy and the team have expanded this gem into a fully laid out and beautifully illustrated book that takes the original game as a jumping-off point into one beast of a game.

Reading the game is an experience in itself, with each page transporting you into a world where eldritch horror mixes with science in a classic horror experience that we've come to expect from Pandion Games. The book is filled with new mechanics, guidelines, lore, tables, and even an illustrated bestiary. I'm excited to bring this game to my table when it is complete and guide my players into the abyss of the Earth trying to save humanity, whatever the cost may be for their characters.
René-Pier Deshaies-Gélinas
Game Designer, Fari RPGs


Reviews and actual plays are already streaming in! Check out these videos and articles to see how our early players feel about the game. As more are released, we'll add them here.

Going Questing, Session 0 and Rules Deep-Dive Review

Interview with RPGs Uncovered

Hammer of the Gods - Character Creation and Overview of Solo Play

Are you a creator that's released an article, AP, review, or podcast about Substratum, and it isn't here? Message us and we'll get it added!

Pandion Games is a game design studio that makes nostalgic collaborative games. Founded in 2021 by Andy Boyd, and nestled in the southern Blue Ridge Mountains, Pandion Games has published seven games to date.

  • Storyteller: A Campfire Narrative Game has players reignite the tradition of telling ghost stories around the campfire with whatever equipment they have on hand.
  • Monsters & Counselors whisks players away to summer camp as counselors, saving their campers from themselves and the dangers that lurk.
  • Banda's Grove envisions campgrounds converging from across the universe to form Banda's Grove and all the wonderful and strange mysteries that ensue.
  • Whispers in the Walls 2e is a solo game of a private detective with the unique ability to understand what the walls remember.
  • Waffles for Esther is a solo mystery game of small-town hijinks as players discover what happened to their favorite diner regular: Esther.
  • The Jester King's Dance, where the player follows a wretched soul who awoke in hell and must rediscover his evil deeds.
  • Badger + Coyote 2e, the cozy Sunday afternoon duet game. Thanks to all our supporters, who helped us create this deluxe and expanded edition in our last Backerkit campaign!

In January 2023, Pandion Games successfully crowdfunded and fulfilled The Dungeon Year Journal, a 365-entry writing and design journal as part of the Dungeon 23 one-a-day challenge.

Check out Pandion Games's store. We are also on

Andy Boyd is the owner and game designer behind Pandion Games. He has a love for old summer camp nostalgia, and the outdoors in general. Growing up, he spent many hours playing point and click adventures games and is where his love of storytelling grew. His games draw inspiration from some of his favorite shows and games such as Gravity Falls, Outer Wilds, Grim Fandango, The Longest Journey, Psychonauts, Over the Garden Wall, and Hilda to name a few.  Andy loves finding just the right mechanics to pair with the different types of stories each of his games explores.

The first book Andy ever published - Storyteller - will always hold a special place in his heart.


Shipping will be charged separately
The estimated cost will fluctuate based upon your pledge level. Below are estimated ranges based on the different tiers we have available. Some add-ons, such as additional game books, may increase shipping beyond these estimates.

  • US: $5-$12
  • CA: $12-$16
  • Rest of World: $16-$20

International Shipping
We ship internationally. However, individuals are responsible for VAT and import taxes for their individual countries. The games ship from the United States. Pandion Games does not collect, remit, or reimburse for incurred VAT or import taxes.

When will you ship Substratum Protocol?
The game is 90% complete already. We will be ready to submit the books to the printers shortly after the campaign ends. Printing and shipping can vary wildly depending on a number of factors, but we expect to begin shipping to backers 2‚Äď3 months after the campaign wraps up.


This campaign is to raise funds to bring Substratum Protocol to life. We work very hard to reduce the risks of publishing and fulfillment.

For the game itself, the writing and layout is mostly complete. We operate our own store and have fulfilled a crowdfunding campaign before, so we feel confident we can provide a quick turn around fulfilling this campaign. Packaging and shipping are already planned and organized for this campaign.

If the campaign does extremely well, we have relationships with fulfillment partners, such as Indie Press Revolution, and will reach out to them immediately if it looks like the campaign will go beyond what we're able to fulfill in a reasonable time.

We purposefully have not created any additional physical stretch goals to keep the complexity of the campaign to a minimum and not delay fulfillment of the game.

Interested in the nitty-gritty of everything Pandion Games is working on?

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