The Shadow Weave
Just as Mystra controlled the Weave, the goddess Shar created and maintained the Shadow Weave as an alternative conduit to magic. Not satisfied with her portion, Shar plotted to seize control of both when Cyric murdered Mystra. She miscalculated. The Weave collapsed so completely that Shar not only failed to gather up its fraying threads, she also lost control over the Shadow Weave. Just as magic persists without Mystra, so does the power of shadow endure without Shar’s intercession. Powerful necromancers have developed their own unique methods for harnessing the dark energy of the Shadowfell.