"Acuere." The pointy end twinkled as the sharpening spell honed the edge. She dragged the blade across Bellatrix’s wrist, in the same spot that the Dark Witch had carved into Hermione. Blood welled out of the wound and dripped down Bellatrix’s hand. Using the vial, Hermione caught a large drop off her fingertip and stirred it into the thick sky-blue potion. It marbled, eventually turning as black as death. 