You poor unfortunate, Prince of a realm so near to my own, so rich in its resources where we have begun to exhaust our own. Oh yes, we as nobles can admit we know that the provocation that my heralds cited was manufactured. Your dear uncle was framed in leading his house troops into my lands, but that was good enough. And besides, now he is dead and the deed was done. It was not by chance that your father the King was separated from his chivalrous guard in the midst of battle - the captain was well paid to do so, and has ambition to serve me in a greater capacity than he could under your father.
You fought well, my Prince, the eldest son of the line. You lie in my castle, well treated by my mute healers, but consider yourself a guest with restraints rather than a prisoner. There is much we can yet discuss. I know you lie here, ignorant of what has transpired since your were taken, but all you need know is that I am here and I am now the one who holds your life in my hands.
Your people call me a Sorceress, and there is truth to what they say, but there are things I will not compel of you with magic, but that I will have of you... one way or another.
(the magic side of fantasy could be there or not, depending on what you're looking for)