Was it stated anywhere (or even hinted at?) that the Sepulchre has any Powers to be Unlocked like on a PoP? Or for that matter that the Sepulchre is even On a Death Lay Line?
What other POP could Nien have owned? Seems like the Litch only has felt the Death energy place.. in the Sepulchre so probably there is Death leyline there.. "Heart Crystal of the ShadowTrench. "
Shadows trench is the name of the pop the deathknight controled. We have no idea where that is, only that the vampires live there.
An additional strategy to grow and strengthen the Mist Village. Ricther needs to gather a few of all types of magical seeds and plants that he can find. Then those plants should be planted as close as the can in or around his dungeon and his place of power. Taking naturally occurring plants that contain herbal abilities or magical abilities then exposing them to higher ambient energies should magically fortify those plants.