When Darkness Falls — William G. Davis

The Dead Zone is an area of the Milky Way from where no ship returns. Intransigent believe they know who controls it. For now, it is not a threat to them, only Imperial Majesty Abaddon, who has lost more than half his star systems. Seeing an opportunity, Areus makes a desperate attack against Imperial Majesty Abaddon by sending thousands of Saiphs and starships into his territory; Intransigent suffered severe losses. Before abandoning their home, Intransigent makes a temporary deal with the ruler of the Dead Zone, but Imperial Majesty Abaddon kills him or her soon after, allowing him to bring total darkness to the galaxy. With no one to stop him, Imperial Majesty Abaddon gives the Night Lord a foothold in our universe.