Ok, so:
A demon cursed him, making him have incredibly lûstful dreams, at first it was just what the demon looked like, then the demon found that changing into any male the prince talked to/looked at fûcked with the prince a whole lot more. So every night, when the demon comes, he changes shape/form to match a male which the prince conversed/looked at to fu** the prince over tenfold. That make sense now?