Substratum Protocol

Descend. Learn. Survive.

The Substratum Protocol was created in the event that an emergency subterranean expedition was ever needed, coupled with the list of scientists, equipment, and procedures to ensure its success regardless of the nature of the emergency.

When the interdimensional portal appeared at the Earth’s core, the Substratum Protocol was initiated and scientists were rushed at all costs to the hastily built Fracture Observatory.

You are the best and brightest scientists we have left to stem the apocalypse. 

You are the Substratum Expedition Team.

What is Substratum Protocol?

Substratum Protocol is a Solo+ survival mystery TTRPG utilizing step-down dice and card draw mechanics. Playable as both a solo game or guided by a GM, players take on the role of the earth’s best remaining scientists. On their grueling journey to the earth’s center, the expedition team will overcome challenges, gain clues and knowledge of the portal, discover creatures, aliens, cosmic horrors, and ultimately assemble their Final Hypothesis to overcome the apocalypse that stands before them and close the portal.

Substratum Protocol uses the Hints and Hijinx system, a purpose built TTRPG system for running solo and multiplayer mysteries where the answers are not predetermined, but up for the players to deduce and - with enough clues discovered - solve the mystery in a grand finale just like our favorite Sherlock, Poirot, and Scooby-Doo mysteries.

This is our entry to the Deep Delving Mystery genre like Subnautica and In Other Waters.

Game features

• Purpose built system for solo and multiplayer mysteries
• Unique dice and card draw resolution mechanics
• Take special Actions whose outcomes 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 you've learned all you can, and are ready to try and stop the portal, work with your other scientists to pour over your knowledge of the portal and construct your Last Hypothesis. Will it be enough?

What others are saying

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 horrors 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

88 page, 6 x 8.5 inch, full color, hardcover book w/ bookmark ribbon. Digital package with PDFs included.

Bundle this with the Solo Journal Accessory Pack for a special price with our Substratum Protocol Solo Journal Bundle