Prisoner of the Heart

She saves his son, so he falls in love with her, she shows him her power and her knowledge, and he convinces her father to marry her off to him. Thranduil makes the princess of the water world his wife, against her wishes and uses force and power to get her to bend which only pushes her into the arms of Legolas. The Elf king sees this and tries to use new methods to win her heart.