Electric Vengeance

Evocation [Electricity]
Level: Sorcerer 2, Wizard 2,
Components: V, S,
Casting Time: 1 immediate action
Range: 5 ft.
Target: One creature
Duration: Instantaneous
Saving Throw: None
Spell Resistance: Yes
Source: Player's Handbook II

As the creature strikes you, an arc of lightning springs from your body and blasts the creature in return.

You can cast this spell only when another creature has just dealt hit point damage to you with a melee attack.
When you cast electric vengeance, a blast of lightning arcs from your body into the subject's; the arc deals 2d8 points of electricity damage +1 point per caster level (maximum +10).