He was intimately familiar with the experience of being interrogated under the Cruciatus curse, and the resulting physical aftereffects. She was washing her face in the sink, shoulders hunched inwards as though she were protecting herself, and when she reached for a towel, her hands trembled. Those familiar with the Cruciatus called it the quivers—lingering little shivers that settled in the extremities, trembling hands and feet that made a full range of motion nearly impossible. The longer one was held under a Crucio, the longer the quivers lingered. On cold mornings or long days, Severus felt the sensation settle in his knees and the knuckles on his left hand; like water, they seeped into old injuries and settled there until it calcified. 