The Weave

The Weave, controlled by Mystryl or one of her successors, is a way through which raw magic was accessed, tapped into and used by casters of magic. The Weave is the way in which magic presents itself to beings for their use, and it flows throughout the world, touching almost every corner of existence, with the exception of dead-magic zones. The Weave coexists with the Shadow Weave.
The Weave is considered many things, including Mystra's body, the source of magic, all the studies of casters, arcane and divine alike, and the many energies and forces that exists around the planes. Many see it as a "fabric" on which magic is "drawn", and damaging the fabric causes magic to go awry. Older textbooks deliberately falsify or outright leave out the nature of the Weave, as an attempt to limit the knowledge associated with spellcasting.