No one ever said the Dark Lord was all teddy bears and kittens...

"Something..," he mutters. Yes. That's it. That has to be it. The door permits people to leave but that person has to be himself at the time in order to leave. If Rodolphus was something he wasn't normally he'd never leave at all.

"Draco I do believe you're onto something. We could turn Rodolphus into something effectively too useless to be of any worth to the Dark Lord. Something small. Something harmless."