The Sundala Starzone / Between Worlds Crossover

An ancient alien race which had mastered all manner of technologies and may have even ascended into a higher dimensional state of existence or simply vanished from some catastrophe or another. It is assumed they 'hollowed out' the dark matter cloud in which the starzone resides, terraformed or even shaped the star systems in which humanity now resides, and built the FTL gates that link them all together.

A wide reaching area of space that was formerly of the Sinopact’s Spinward frontier with the KSPN, a large swath along that border now represents the sole holdings of the now rump of an interstellar power. A few hundred million now dedicated to taking back their systems from the Shil’valti occupation. Their fervor fanned by propaganda depicting the starvation and deaths during the invasion as solely the fault of the Imperium, slowly pushing the Sinopact’s own follies out of view.

Supported by the backing and economic support of the Union of Progressive People’s Systems (KSPN in Russian acronym) they have effectively made all of their former holdings within range of their vessels impossible to colonize or even exploit. Conducting near constant raids and low level attacks against Imperial interests in the area and forcing the Imperial Navy to maintain a significant fleet to keep these exploratory raids bottled up. While the current entirety of the Imperial Navy presence in the new occupied territories could potentially bring an end to this remnant, it would be costly and would open them to attack from both the American Front and from the Remnant’s KSPN backers. As such they’re trapped, stuck in a tug of war with a fanatical and dangerous remnant they've driven Spinward of their new acquisitions.