A black hole, or singularity, forms when a dying star collapses with such gravitational force that it breaks through the planes and creates a gash in space that sucks everything nearby into a portal to the Negative Energy Plane—effectively mirroring the portals to Positive Energy Planes found at the center of stars. Sceaduinars guard these Negative Energy portals. Other rare occurrences involving powerful entities or artifacts can also spawn black holes.
Black holes' concentrated negative energy causes nearby undead to become more powerful, and their destructive forces attract planet-sized nightshades.
The now-insane scholar Fulvia Nostraema wrote an essay, "Nihilism's Sacred Garrote," describing how the Dominion of the Black uses black holes as part of a ceremonial sacrifice ritual known as the Banquet, where the Dominion casts scores of creatures—and some of its own living spaceships—into the black hole's all-consuming gravitational well.