Where dead things are...

There is no Oblivion on Balkar, and no Underworld in the spiritual sense (a physical one exists, though). The place where the Malfeans, the fallen Primordials, were killed still exists physically, and though their material corpses are no more, their influence can't be mistaken. For centuries after the great war, this place drew battles like a flame draws moths. Slaughter after slaughter, Kings and peasants alive disappeared by thousands, buried in necropolis built to celebrate battles quickly forgotten or simply swallowed by a blood-drenched earth.
None battles here anymore, for the place is rightly known as the Moors of Sorrows. But the Dead, both mortals and divine, are still here. The Malfeans still dream, but their dreams are now nightmares of stasis and decay. For all of Balkar's known history, more necromancers than it's possible to count tried to gain control of the Moors, and all have underestimated the magnitude of the task and died. Recently, though, rumors from all countries around the Moors point to striking similarities between the usually erratic behaviors of the Undead. Some think, and fear, that at last a necromancer has reached the Graal of his or her kind. There is some truth to it, for there is indeed a powerful Necromancer, but he is only a curtain behind which the Deathlords plan to hide the true extent of the threat they represent. Such a role of strawman and target to each and every undead slayer doesn't exactly satisfy the Necromancer, but he knows firsthand the might of the Deathlords. More, he knows the true power behind them, and plans to contact them and offer them his services. It will take time, both to find a way around the jealously guarded accesses to the Malfeans' resting places and to grow the power needed to get the slumbering Primordials consider him, but what is time for he who holds Death at his beck and call ?
Though they despise him for being merely an upstart mortal Thaumaturge and don't trust him one bit, the Deathlords know the Necromancer has invaluable insight in modern society. They also are dependant on his cult network, established well before the Necromancer waded in the Moors, for spying and recruitment.
That is, as long as they are not strong enough to securely reveal themselves. Until then, their servants the Abyssals, unsuspectable weapons, hone their skills, patrol the Moors and for some of them, scout the ouside world, hiding behind the appearance of living their quest for generalized death.