Tempest Magic

Heroic Tier
Prerequisite: Sorcerer, Con 13, Dex 13, Storm Magic class feature
Benefit: When you use an arcane power that has the lightning or thunder keyword, you gain a +1 feat bonus to damage rolls. While you are bloodied, this bonus becomes +2.
At 11th level, this bonus increases to +2 (or +4 when bloodied). At 21st level, it increases to +3 (or +6 when bloodied).

Published in Arcane Power, page(s) 129.