Netherworld

The Netherworld, also known as the Shadow Plane, is a result of various beings from the Void, especially Murskuug - Avatar of the Void, attempting to meddle with The Creation of the Material Planes. Aedifidea - Planar Architect and Tempmet - Time's Arrow / Moons' Keeper were able to construct a separate plane to keep all of the Void's twisted creations in. As a result, the Shadow Plane is copy of the Material Plane devoid of all light and contains its own twisted version of living beings, both humanoid and monstrous.