A succubus

You had just won a battle over a wizard lord who fought for your enemy. When ransacking his possessions, you found he had a succubus chained in his bedroom.

Succubi were demons of lust. They always looked female, had well developed curves, possessed good looking facial features and also always had a cock. They would please man and woman alike in any number of ways.
You decided you should keep this one for yourself.

You had her brought to your castle and had her chained up in your own room. There she would remain and pleasure you whenever you felt like.
Finally, after such a long time after you captured her, you find the time you needed to have some time alone with her.