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Concussive Spell (Metamagic)
You cause creatures to be disoriented when you affect them with a spell that has the sonic descriptor.
Benefit: With sonic damage comes a concussive wave of energy that rattles creatures affected by the spell. A concussive spell causes creatures that take damage from a spell that has the sonic descriptor to take a –2 penalty on attack rolls, saving throws, skill checks, and ability checks for a number of rounds equal to the actual spell level of the spell. A concussive spell only affects spells with the sonic descriptor. A concussive spell uses up a spell slot two levels higher than the spell's actual level.