You will stroke that cock for your Mistress, but I will not allow you to cum. You will play with those balls, full of hot cum, but I will not allow them to unload. You will be completely under my spell, with your swollen head and throbbing shaft, but you will not be granted an orgasm. You will be denied such pleasures because that is what I see fit, and you have no choice but to obey your Mistress, and be left in a state of maddening horniness. A state where you can be completely controlled and manipulated by me, the granter of Ejaculation.  Teased mercifully to the point of exhaustion, begging for relief.  It'll only come when I feel it's time.