Amenti Raven appears in the 2nd through 4th Chapter of the Void Quest within the Midnight Channel. They will alternate between attacking and using Power Charge then attacking. Upon being defeated, Amenti Ravens may drop the Devilish Feather material. Selling 6 Devilish Feathers at Daidara will unlock the Madam's Charm ougi for Yukiko Amagi in the shop.
In Golden, it may also drop Lemon Quartz for trade at Shiroku Pub.