The Nightmare Dragon

From the introduction: Soaring through twilight, Nightmare's hide in the shadows hunting those they deem corrupt. Born the twisted spawn of Ift, their righteous delusions lead them to strike at anyone, no matter how good or evil. Unlike some of their more destructive relatives, they tend to obsess over individuals. Often their efforts are so focused that they become ignorant of other threats while attempting to exact their cruel form of justice. When faced with another dragon, this obsession is magnified to the point of cannibalism to ensure that nothing remains of their prey.