'And if I told you my little spell is designed to keep them from knocking in the first place?' Cass said with a smirk. 'Unless it's an emergency, no one is going to interrupt us,' he said. Really what did Percy think went on in the Slytherin common room, or locker rooms for that matter? Keeping people out was necessary. Especially Monty when you were doing Higgs. Merlin he would have fainted.
'Have you seen her when she fully applies herself?' Cass asked. 'She can disguise herself to perfection, morph into any shape she wants. And no, she wouldn't have access by looking like one of them, but she could use the disguise to gain trust and show support for them. It's slow, naturally, and about a million things could go wrong, but if it succeeded, wouldn't it be worth it?'