The Negative Plane is a plane of existence that serves as the realm of undeath and necrotic energy.
Role in the Adventure
The Negative Plane is referenced as the origin point of the atropal — the central threat powering the death curse. Acererak, the powerful lich antagonist, discovered this atropal “adrift at the edge of the Negative Plane” and subsequently constructed the Soulmonger to nourish it toward godhood.
Significance
The Negative Plane represents the source of the atropal’s undead nature and its connection to death magic. By finding the atropal at the boundary of this plane and bringing it to Toril, Acererak set in motion the events of the adventure — the creation of the Soulmonger within the Tomb of the Nine Gods and the resulting death curse that prevents resurrection magic from functioning.
The plane itself is not visited during the adventure, but understanding its connection to the atropal provides important context for the nature of the threat the characters face: they are ultimately confronting a nascent god of undeath that originated from the plane where death and negative energy hold dominion.