Book: The Taken King.
“What the forge does to your Light must be respected, and feared. That path is not for everyone. The Sunbreakers take the oath very seriously. I’m not trying to talk you out of anything. I’m just making sure you know the stakes. That forge breaks the brittle. And it bends the weak. But the strong, the strong walk away steeled and tempered. Unbreakable.” - Lord Shaxx