She was the perfect bride, till she realised she wanted to be more. More than just a trophy wife for a king who didn't care. More than a woman that will be forgotten as soon as she died. She became a warrior to fight for her beloved.
I actually really like Emma Stone, but being a redhead (or at least often-dyed-red-head) with a crazy gleam in her eye, she'd do a good job as the psychotically deadly Krystal who joins Thanatos in book 2 (Underworld's Daughter).