Evil Brand( Fiendish Codex I: Hordes of the Abyss, p. 85)
You are physically marked forever as the servant of an evil power greater than yourself--in this case, a demon lord. The symbols is unquestionable in its perversity, depicting a depravity so unthinkable that all who see it know beyond a doubt that you serve the lords of the Abyss.
Evil creatures automatically recognize the symbol now emblazoned upon you as a sign of your utter depravity or discipleship to a powerful demon lord, although the brand does not necessarily reveal your patron's identity. You gain a +2 circumstance bonus on Diplomacy and Intimidate checks made against evil creatures.