unique origin and galaxy gen, dunno how stable the game is with multiple wormholes per system. habitable worlds would be on the perimeter with underground survivors in pre-FTL states , their population having went deep to survive. the galactic center being a huge blackhole system.

as part of an emergency denial operation undertaken by the previous inhabitants of the galaxy, they had to sacrifice 70% of the systems, the hyperlane network was blown apart by the blast and things just generally went to hell. the scattered survivors having had to readjust to this new hyperlaneless galaxy and retool all their tech.

the crisis event , obviously being extra dimensional invaders, tearing themselves free of the blackhole and swarming out through the various wormholes. the wormholes were setup by the curators, with gateways having been destroyed in the blast or crippled so exhaustively it was too difficult and unsafe to restart them so early afterwards, a wormhole generator based on a massive psionic jump drive tech maintained a stable wormhole, the one downside being the recalculations needed by each empire to safely travel - an acceptable trade off.