Several years have passed since Coriana VI and the departure of the Shadows and Vorlons from the galaxy. Finally, the younger races are free to find their own paths without the presence of the First Ones. Or are they?
Scout ships recently found a strange zone of hyperspace just beyond the rim of known space. Hyperspace seemed to fold in on itslef here in a strange fashion forming an isolated pocket tens of light years across. Further investigation revealed that the ancient races had not quite kept their word. Within this bastion the Shadows, Vorlons, and a cadre of lesser servants continued to secretly keep tabs on the progress of the galaxy.
Seeing this as an affront - and a violation of a promise - several of the galactic powers dispatched fleets to show the first ones that they were no longer needed and (more importantly) no longer capable of enforcing their will upon the galaxy. Twelve fleets were sent, one from each major participating power. Nine were lost in the tides of the hyperspace traps guarding the entrances to this zone.
The three surviving fleets each established a foothold in an outlying system. As the Shadow homeworld was destroyed and the Vorlon homeworld impenetrable, this represented a unique opportunity to capture and study First One technology. What began as a join effort to evict the straggling First Ones out of galactic space quickly became a race for each fleet to capture technology and information...and to prevent their rivals from doing the same.
The unique, isolated pocket of space contained thirteen systems linked by a local jump gate network. Each of the three invading fleets laid claim to one of the three "entry systems" along the periphery. The rest of the systems were in various states of occupation by the Shadows, Vorlons, and their servants.