Lure ancient spirits to bargain for their power. Secrets of Pact Magic is a complete guide for the use of pact magic in your d20 System game, as inspired by medieval Goetian magic. A pact mage summons an ancient spirit to bargain for the brief use of its terrible power. Over one hundred spirits, including elemental and epic spirits, wait to be bound. Each spirit receives a two-page layout with geometric seal, legend, ritual, granted abilities, side-effects, tactical bonuses, and more. A spellcaster can swap spells for a spirit. Included are new races and base classes such as the pact warrior, occult priest, and unbound witch. In addition to feats, spells, prestige classes, creatures, and magic items, thirteen organizations are keyed to constellations of spirits. Game masters can send players to the Apocryphal Desert, the Ravaged Sea, and the Outer Darkness. Includes tools to quickly generate NPCs and design new spirits. Requires the use of the Dungeons & Dragons Player's Handbook, v3.5, published by Wizards of the Coast, Inc.