From the back of the book:
Spellcasters enter into battle wearing full armor, wielding spells that can fell cities. Wizards join together to cast spells of unbelievable might and power. Mages cast spells from memory without the need to restudy them. Players create their own spells!
The Codex Mysterium introduces new rules for magic and spellcasting, as well as a unique formula that allows players to create their own spells, all fully compatible with the fabulous d20 System. Designed for use within the Sovereign Stone (tm) world, this new magic system, new spell creation formula, and new spells may all be used with any campaign setting in the d20 System.
Within these pages, you will find over two hundred new spells for Elemental and Void mages, new prestige classes, new rules for spell creation for use with the d20 magic system, plus further information on the magic-users of the Sovereign Stone world, including the powerful battle-mages of the Temple of the Magi, the mysterious and powerful Elven Wyred, the mage guilds of Dunkarga, the devoutly religiuos Nimran priests, the rampaging Dwarven Firemages, and much more!
Open the book to uncover the mysteries of magic!