A mixture

A nun entered the room and removed the crotch strap. Rebecca was relieved, and awaited the removal of the "Iron Maiden."

But the metal stayed on.

She waited for a moment, and soon felt a large cock sticking itself into her cunt. It fucked her gruffly, but she felt incredible. Another dick entered her mouth, but she sucked at it hungrily. A third cock, thicker than the other two and unlubricated, shoved its way into her ass. She would have screamed in pain, but the penis in her mouth muffled her shouts. As each cock came, it was replaced by a longer, thicker one. By the third new cock in her ass, Rebecca felt she would explode.

An unknown amount of time later (it seemed like a week to Rebecca) all dicks were removed, and the crotch strap, refitted with mammoth dildos, was replaced. Rebecca wondered if her hell was almost over, but also wondered about her predicament. 'Will the next cocks be bigger?' she thought, 'Ooh, I hope so!' she found herself saying.