You lower your weapon, allowing your opponent to score a glancing blow, but the pain only fuels your rage and adds strength to your own attacks.

Encounter   ✦     Primal
Minor Action      Personal

Effect: Each enemy adjacent to you can make an opportunity attack against you. Until the end of your next turn, you gain a bonus to attack rolls equal to +2 for each enemy that makes the opportunity attack.

Published in Player's Handbook 2, page(s) 57.