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 community compendium of house rules for The Mothership Sci-Fi Horror RPG. This book defines a full methodology for solo and Wardenless play and includes house rules for everything from downtime to cybernetics.