Sunless Horizon

Sunless Horizon is the most self-indulgent setting I'll ever make, taking inspiration from Veins of the Earth, Axis Mundi, HMS Apollyon, Rain World, Orion's Arm, and Duskers.

The stars are dead. As the universe collapsed, humanity built Ein Soph: a worldship controlled by a network of AIs intended to keep operating until the AIs could find a way to dig into a new universe.

That was thousands of years ago.

The AIs have all been subsumed by Keter, who sealed the last of humanity into the Empyrean: a 20-mile long O'Neill's Cylinder under his direct supervision, "ruled" by the Prophetess Maia.

Outside of the Empyrean, castoff biotech projects have grown into their own species, laboring under the feudalistic Navigator Houses, who say they control Ein Soph, and that they're headed to Heaven.

Keter's protective programming extends only to humans, not to his creations: his androids tear at the borders of the Navigator Houses as he gets ever closer to pulling open reality.

Keter's Infopriests lead pilgrimages across the Coolant Sea atop their walking altars.

Rumors abound of the unnatural technologies Keter can bring to bear: Tipler Oracles, memetic plagues, non-euclidean creatures, and nanobot swarms.

Outside of Ein Soph, the universe is dark. The stars have all burned out. However, fragments of Ein Soph's supporting fleet orbit around the worldship in a halo-shaped mass called the Crown. Expeditions by the Navigator Houses have never returned, but that doesn't stop whispered discussion of what could live there. Some say the Crown is Keter's final defense, preventing any escape from Ein Soph.

The weapons of the peasants are crude and ineffective.

The Navigator Houses send missions out into Ein Soph to gather resources: these expeditions cross paths with Ghoul Nests, Keter's Disciples, and the creatures that have evolved to live in this hellish, lightless environment.

The Disciples scrawl strange symbols on their travels. Some can kill.