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The martial keyword indicates that the power source of a class or power is martial arts training and physical prowess.

Martial: Martial powers are not magic in the traditional sense, although some martial powers stand well beyond the capabilities of ordinary mortals.[PH:54]

Classes that draw power from the martial power source are:

Martial powers are also called "Exploits."

The other power sources are Arcane, Divine, Primal, Psionic, and Shadow.