Ancient Soul

Heroic Tier
Prerequisite: Dragonborn, Dragon Magic sorcerer, dragon breath racial power
Benefit: Your dragon breath power is considered an arcane attack power.
In addition, if your dragon breath power deals damage of the same type as your Dragon Magic class feature gives you resistance to, you gain the following benefit:
Whenever you take damage of the type dealt by your dragon breath (after the damage dealt is reduced by your resistance), you regain the use of your dragon breath if you have already expended it in this encounter.

Published in Player's Handbook Races: Dragonborn, page(s) 22.