Evil Devotion( Complete Champion, p. 58)
The power of evil cloaks you and your allies.
Once per day as an immediate action, you can surround yourself with an aura of evil that grants you and each of your allies within 30 feet damage reduction that can be overcome only by good-aligned weapons. The numeric value of this damage reduction is 1 + 1/five character levels you possess maximum 5/good at 20th level). In addition, your and your allies' natural and weapon attacks are evil-aligned for the purpose of overcoming damage reduction. This effect lasts for 1 minute.
You can select this feat multiple times, gaining one additional daily use each time you take it.
If you have the ability to turn or rebuke undead, you gain one additional daily use of this feat for each daily turn or rebuke use you expend.