Night Triumphant - and the Stars Eternal.
If he was the sweet, terrifying darkness, I was the glittering light that only his shadows could make clear.

...are you as deft at handling your sword as Captain Westfall?"
"Better," he whispered in her ear.

She knew he meant it. He’d burn the library, the city or the whole world to ashes if she asked him. It was their bond, marked by blood and scent and something else she couldn’t place. A tether as strong as the one that bound her to her parents. Stronger, in some ways.

He stalked closer, his movements feline, those violet eyes turning subdued-lethal. "You're welcome, you know."

"For saving you when asked." I stiffened. " I didn't ask for anything.

Because the stag remains constant–no matter the season, he's always there."
"Why?"
Celaena took a long breath. "So the people of Terrasen will always know how to find their way home, So they can look up at the sky, no matter where they are, and know Terrasen is forever with them.

The stag’s enormous head turned slightly—toward the wagon, toward the small window.

The Lord of the North.

So the people of Terrasen will always know how to find their way home, she’d once told Ansel as they lay under a blanket of stars and traced the constellation of the stag.

So they can look up at the sky, no matter where they are, and know Terrasen is forever with them.