Underzone

The Underzone is a "pocket universe" or "basement universe" thought to have been created by the Geometrician paleocivilization over three hundred million years ago. Intended as a fast means of interstellar transit, it is now an eerie realm of gravitational distortions, shears, and random debris, back-dropped by a starless void. Access to the Underzone is accomplished through Jumpgates found in various locations in the Starweb and beyond.

Characteristics

Each Jumpgate in normal space connects to a counterpart in the Underzone, from which ships arrive nearly at rest. From there, travelers can locate their destination Jumpgate and proceed through it. This has the advantage that, unlike the Starweb where a lengthy trip may involve several periods of acceleration and deceleration to cross multiple solar systems and their stargates, the Underzone provides a single area in which all destinations can be accessed.
The catch, they say, is everything else. In its early days it's thought the Underzone was a sedate realm, with gravitational contours shaped to guide ships in coasting from gate to gate, but 300 megayears of neglect have transformed this into a twisted mess of gravitational shears, the worst of which can rip apart a ship down to the molecules. Debris, ranging from asteroidial pebbles to dwarf planets, is not uncommon, nor is wreckage from ancient spacecraft.

The Underzone's full extents are unknown, only that within it distances are greatly contracted: a pair of gates orbiting stars separated by lightyears may have their counterparts only a few million kilometers away in the Zone. It is possible the gates within it lead to apertures across the galaxy, or even beyond, though no one in the modern day has ventured anywhere near that far.

An entire galactic rotation has passed since the Underzone's creation, scattering many once-close stars far away from each other, yet within the Zone exit gates still connect to nearby ones. It is theorized that gates within it move around in response to stellar drift in the "normal" universe, ensuring the closest gates remain connected to the closest stars.

Features

Completely devoid of stars, the Underzone is incredibly dark. Ships instead visualize their surroundings with gravimetric sensors or active scans; the only other light being the eerie red glow of exit-gate rings. Safe passages are painstakingly mapped out and denoted with navigation buoys, these can be calm "tunnels" or intense tidal "rapids" which shake and rattle vessels as they pass through.

Origins / History

Creation of the Underzone is commonly attributed to the Geometricians, as their ruins tend to be found in many, though not all, systems containing a Jumpgate, and other Geometrician technologies display evidence of highly-advanced spacetime engineering. However, not all xenologists are convinced, and some assign its origins to an even more ancient civilization, like the Space-Weavers. In support of this, they point to natural debris, mostly asteriodial rock, discovered in the Underzone and dating back billions of years. Opponents counter this proves nothing, such matter could've simply fallen through the Jumpgates after the Zone's creation. No direct evidence exists either way.

The Underzone was used by successor paleocivilizations before the rise of humanity and other Starweb species, such as the Priors and, presumably, Hexamites.