"If it isn't the mudblood lover and his pets," Rosier sneers down at them, looking particularly nasty when Dorcas meets his gaze. "I didn't think they allowed animals into the library."
Dorcas feels anger bubble up, but forces herself to take a moment to consider her options. She doesn't remember much of Rosier, only really vaguely recognizes his name, so there's no telling how important he was to Voldemort's movement. He is in Slytherin, though, Voldemort's main recruitment pool, so she thinks he might be worth swaying to her side.
Outright friendliness hadn't worked on him the first time, and neither had defiance. Maybe...
"How'd you do on the Charms test last week?" Dorcas asks abruptly, completely dismissing his insult. She sees him wince, and she knows she has him—how lucky she is to have been present in time to hear him complain loudly in the halls the other day about how 'utterly useless and ridiculous' a subject Charms is. "We'll help you study if you help us in return."
She can feel the bewildered stares of her friends, but she does nothing to clear up their confusion, simply continues staring at Rosier expectantly.
"Why would I want your help? You're just a mud-"
"Lily and I have top marks there," Dorcas cuts him off, raising an eyebrow. "Come on, we could use your help in History of Magic. You were right, there are just some things you understand better when you're born into magic."
A bargain plus an appeal to his sense of superiority. Simple but, assuming he takes the bait, should open the doors to better opportunities for her to take advantage of later.
He seems to hesitate, and Dorcas feels a sense of triumph. After all, if he were completely against the idea he would just leave.
As a final incentive, Dorcas shoots him a challenging look—equal parts daring and arrogant—and the boy immediately squares his shoulders, shooting the three of them a haughty smirk.
"Well, of course you'd need my help."
Ah, kids can be so simple sometimes.
AN: Dorcas really isn't as good at manipulating as she thinks she is. Anyone older than the age of maybe sixteen would probably see through her, lol.