In the mirrors around them, Emilia saw visions of what Belial was promising, of all that his cure would mean. The woman Brother Zachariah adored would not be alone. He would be with her, able to share her pain and to love her wholly once more. He could rush to the side of the friend he loved, see his friend’s blue eyes shine like stars on a midsummer night as he beheld Brother Zachariah transformed. They could clasp hands with no shadow of grief or pain upon them, just once. They had been waiting all their lives for that moment, and feared it would never come.

In a hundred reflections, Brother Zachariah’s eyes flew open, blind and silver with agony. His face twisted as if he were being forced to endure the most terrible pain or, worse, forced to turn from the most perfect bliss.

The real Brother Zachariah’s eyes stayed closed. His face remained serene.

At last he said, The Carstairs owe a life debt to the Herondales. That is my choice.

Belial said, “Then here is what I will tell you about these lost Herondales. There is power in their blood, and there is great danger, too. They are in hiding from an enemy who is neither mortal nor demon. These pursuers are resourceful, and close on their heels, and they will kill them if they find them.”

“But where are they?” Sister Emilia said.

Belial said, “The debt is not that great, my dear. And now it is paid.”

Sister Emilia looked at Brother Zachariah, who shook his head. Belial is what he is, he said. A fornicator, a miser, and a polluter of sanctuaries. A creator of illusions. If I had made the other choice, do you really think I would be better off?

“How well we know each other!” Belial said. “We all play a role, and it would astonish you, I think, to know how helpful I am being. You think I have offered you only tricks and sleights, but truly I have extended the hand of friendship. Or do you think that I can simply draw these Herondales out of a hat like so many rabbits? As for you, Sister Emilia, I owe you no debt, but would do you a good turn. Unlike our acquaintance here, you have chosen the path that you are set on.”

“I have,” Sister Emilia said. All she had ever wanted was to make things. To shape seraph blades and be known as a master of the forge. Shadowhunters, it seemed to her, gloried in destruction. What she longed for was to be permitted to create.

“I could make it so that you were the greatest adamas worker the Adamant Citadel has ever seen. Your name would be spoken for generations.”