Dragon scales cover your form in reaction to an assault, as arcane power shields your mind and body from harm.

Encounter   ✦     Arcane
Immediate Interrupt      Personal

Trigger: You are hit by an attack

Effect: You gain a +4 bonus to all defenses against the triggering attack.

  Dragon Magic: The bonus to all defenses equals 3 + your Strength modifier.

Published in Player's Handbook 2, page(s) 141.