Jay Kristoff said this quote

My gift to you, Yukiko-chan.' He nodded. 'Use it to cut away your fear, and leave nothing in its wake. Cherish it. And cherish this truth I speak to you now, if no other before or after: The greatest tempest Shima has even known waits in the wings for you to call its name. Your anger can topple mountains. Crush empires. Change the very shape of the world.'He pressed the blade into her hand, watched her with cool eyes the colour of steel.'Your anger is a gift.