On one hand, you know you will lose a part of yourself if you perform the spell on yourself: if you become evil, everything your fight for so far (peace for the unified human Empire, knowledge for the Adademy of Arcanes) will become your enemy.
On the other hand, what is the point of staying good if you are a powerless prisonner ? At least, if you regain your magical power, you will be able to defeat the Dark Master and you will have your revenge.
So your draw a pentagram, step inside and began chanting. Stranglely, you don't feel any change. You are still the same old you. Well, except that you are still female, of course. You look at your naked body, and you finally understand why other people, those pitiful worms, look at you with envy and fear. They shall admire you, they shall respect you, and they shall obey you. And if they don't, you'll teach them the hard way: by killing some, so that the others bow to you. You grin.
Yes, life will be good. Your ambition and your thirst for power are no longer limited by your morality. The world is yours. You don't feel evil, you feel liberated. You are free to embrace the darkness, to destroy the human Empire and to create your own realm. You laugh. Who are you kidding ? Or course you are evil, and you are proud of that. All those years, you had to pretend being a good person when you were evil to the core. You hate all those people who taught you about moral rules, about helping the weaks, about becoming a hero. Your professors knew nothing. Surely, they were afraid of your greatness once you fully embrace evilness. They feared what you could become. But they failed. Now, it's time to show them the real you.
You are not a hero. You are a vilainess. And so, the second rune disappears from your naked skin. One more rune to solve, and you'll recover all your magical powers. And once you get back your powers, no one, not even the Dark Master, could oppose you. You will become the Dark Queen, all will kneel before you. This dream of absolute power is so sweet, and you pussy feels wet just by thinking about your future power.
So, you don't want to waste any more time so you start to decypher the last rune. 30 minutes later, you know its meaning: it prevents you from casting spells unless you are truely loyal to the Dark Master. If you want to regain your full power, you must perform a Ritual of Loyalty on yourself, which cannot later be broken by any means. In other words, if you do so, you will litteraly belong to the Dark Master: you will be his sex slave, his evil witch and loyal minion, you will fulfill his goals with all your magical power and defends him with your life if needed.
You hesitate, because, as much you hate the Dark Master, and want to be free so you can have your revenge, you also want to regain your power at any cost. Besides, the Dark Master is powerful and so sexy. You desire him. You lust for him. If you join him, the human empire and the Academy of Arcanes will be doomed. What kind of evil can you do if you stay a powerless prisonner ? You know what you have to do. But before you can so anything, someone enters the room where you are held captive. You see ...