Spell power coefficient is an intrinsic property of a spell that determines how much bonus damage or healing it gets from the spell power attribute accumulated from gear, buffs, and talents. In most cases, the coefficient is fixed for a spell; in other cases, it is changed by talents, such as various "empowering" talents, available to some caster classes. Spell power coefficients usually follow set rules outlined in the spell power article, but many exceptions exist. Exact spell power coefficients are tested experimentally and documented when well known.