Elf. Futa Monster Girls, #12

It was supposed to be the moment of their greatest victory, the day they defeated the Evil Empress and put an end to her reign, but the other woman didn't go to her death without a last act of evil. With her last breath, she threw the Curse of Lust at Tessa, and there was nothing the brunette could do to stop it. Then, her mentor, the elf Aela, put herself in the path of that curse and suffered the fate reserved for the brunette.
For a time, Tessa hoped the evil curse failed to take root in the holy knight, but it was too powerful for that. Aela still resisted it and hid the effects it had on her for the most part. The elf was crowned queen by her countrymen, given the power to continue cleansing the corruption the dead witch had spread, but what no one else knew was how changed she had become. How cursed. Only Tessa knew all of it, and only she could do something about it.
Aela had changed, became a futa, and without fail, lust would gather within her until she eventually became overwhelmed and lost control. Tessa did the only thing she could and offered herself to the other female to satisfy her need, her lust. It was the least she could do for the woman she had come to love.