The Ashen Veil is a book revealed in Dishonored: The Corroded Man.
[Excerpt from a private journal]
Sometimes when I sleep I dream, and in those dreams I am many things. I am an adventurer, a traveler. I am a hero and I am a tyrant, a beggar on the street, the ruler of the world. And sometimes in those dreams I see a light, bright and shining, red and golden white, the light of a fire that burned so very long ago, when one world ended and another began. And when I wake the dream is gone but the feeling remains, the echo of song ringing in my ears, the warmth of a winter hearth and the shine of light on a distant, unknown horizon.
This excerpt is quoted at the beginning of Chapter 31.