Type: Metamagic
Source: Complete Mage
You can keep a spell in reserve to use when a foe causes you harm.
Benefit: When you cast a spell modified by this metamagic feat, the spell has no immediate effect. Any time you are dealt damage by a melee attack during the next 24 hours (or until you next prepare or ready your spells), you can choose to cast the spell on that attacker as an immediate action. Once activated, a retributive spell disappears (it can only affect one attacker).
You can apply this feat only to a spell that targets a creature. A retributive spell can target only the attacker that triggered it, even if the spell would normally allow you to target multiple creatures.
You can have only one retributive spell cast at a time. Casting a second retributive spell cancels the first (eliminating it with no effect). If you 3 prepare or ready spells while you have a retributive spell cast, the spell dissipates with no effect.
A retributive spell uses up a spell slot one level higher than the spell's actual level.