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.

A solo+ survival mystery RPG using step-down dice and card draw mechanics, Substratum Protocol is playable as both a solo game or guided by a GM for 2–6 players.

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.

• Purpose-built for solo and multiplayer mysteries
• Unique dice and card draw resolution mechanics
• Take special Actions whose outcomes can chain together
• Collect 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?