Eyes of the Abyss( Fiendish Codex I: Hordes of the Abyss, p. 86)
Your eyes glow with an inner fire of some unusual color. This glow increases your perception and allows you to see in the dark.
Any other Abyssal heritor feat,
You gain darkvision out to a range of 30 feet and a bonus on Search and Spot checks. The amount of this bonus equals the number of Abyssal heritor feats you possess.
Your glowing eyes are disconcerting and distracting to those with whom you interact. This effect manifests as a -2 penalty on Diplomacy checks.