Sarah J. Maas
About the book
But it was the ash wood that made their immortal, healing magic falter long enough for a human to make a killing blow. It was like striding through a living painting—a fleeting moment of stillness, the blues swiftly shifting to solid darkness. Rhysand now faced the High Lord, and his perfect face was void of emotion before his brows rose. They appeared through the cracks from slivers of darkness, just as Rhysand had.