Severus Snape.

Snape is a distinguished potion maker. He perfected potion compositions and preparation methods and could recite the origins, etymologies, and potions by heart. He also invented several new spells, such as Sectumsempra and Levicorpus. He is a master of Occlumency and Legilimency.

Snape was unsociable, abrupt, and unpleasant to talk to, strict with students (especially those not in Slytherin), and picky about the slightest thing. He could, however, quiet a noisy class with a low whisper. He often divided people into "us" and "them" and was prone to paranoid tendencies. As a child, he suppressed his aggression, and as an adult, he felt the need to criticize and punish others.

Snape is described as a tall, thin man with pale skin, a hooked nose, and long, greasy shoulder-length hair. His black eyes were cold and empty, reminiscent of "dark tunnels." He spoke in a soft, low voice with a hint of steel. He preferred to wear black, billowing robes, which gave him the appearance of a bat.