They made their way through the battle raging outside, which was no easy task.  Hermione strained for a glimpse of Lucius, or of Narcissa, or of Yaxley, but she saw nothing.  She was appalled by the sight of Greyback, drinking the blood of Lavender Brown, who was clearly dead.  He looked up and recognized her, and with a lewd grin, blood dripping from his chin, opened his mouth to speak – but she threw a knockback jinx at him before he could, forcing him through the open window.  It wouldn’t kill him, but at least it got him away from Lavender.  She had been relieved for a glimpse of Seamus, Cho, others she couldn’t recognize in the dark, when a man she’d never seen before cast the most powerful Patronus she’d ever seen and sent hundreds of dementors flying back, clearing the path for them.