So secret even its name is a mystery:
Some say the name comes from the Sodality of Vryn, which identifies thirteen currents of magic and gives each a letter designation-M is the 13th and most powerful. Others say the title refers to the original writer of the book, while still others believe it stands for myself, or-perhaps most simple and obviously-magic.
Whatever the source of its name, the coveted Book M is whispered to contain unknown spells, incantations, rituals, charms, hexes, and more. Plus potions, amulets, bezoards, spiritstones, and madstones, as well as other physical ephemera. Within its pages a vislae might even discover previously unknown artifacts to aid in the pursuit of the secrets of reality.