"I first became aware of it, Mandrake, during the physical act of love. Yes, a profound sense of fatigue, a feeling of emptiness followed. Luckily I was able to interpret these feelings correctly. Loss of essence. I can assure you its has not recurred, Mandrake. Women, er women sense my power, and they seek the life essence. I do not avoid women, Mandrake ... but I do deny them my essence."
(see quote in context)