While designed specifically for the Boundless Horizons system, the material in this supplement can be easily adapted to other, similar systems with only minor changes.

Invocation Magic is focused, as the name might suggest, on invokers and their invocations. Invocations are an alternate form of magic that is more limited in scope and power than the traditional magic sources, but can also be used at will, rather than through the use of spell slots, power points, or any other limiting measure (other than action economy).

This supplement introduces five invoker base classes, each themed around a different power source, 6 new prestige classes, and adaptations for 5 existing prestige classes. There are roughly 100 defined invocations to choose from (though each particular class has limitations on which ones can be chosen -- each invoker class has roughly 50 of the invocations on its class list). There are also some invoker-specific feats and magic items, and even a new bestiary entry (along with a few modified ones).

Guidelines are also provided for creating and adapting other classes and for making new invocations, etc. For games where invokers are meant to replace traditional spellcasting, invoking versions of the Bard and Ranger base classes and the Assassin and Champion prestige classes are provided.