in memoriam to the most loyal member of the order

Professor Severus Snape (January 9, 1960 – May 2, 1998) was Potions master (1981–1996), Defence Against the Dark Arts professor (1996–1997 school year), and Headmaster (1997–1998 school year) of Hogwarts School of Witchcraft and Wizardry. Snape played an important role in the war against Voldemort, though he did so covertly and at great personal risk.
He was a half-blood wizard, born to Eileen Prince and Tobias Snape. Severus was raised in the Muggle dwelling of Spinner's End where he was in close proximity to Lily and Petunia Evans. Severus fell deeply in love with Lily at a very young age. In 1971 he began his first term at Hogwarts where he was sorted into Slytherin. Severus became the immediate enemy of James Potter and Sirius Black and was a frequent victim of their bullying. Snape developed a passion for the Dark Arts and pure-blood supremacy, despite his love for Lily, a Muggle-born. Both put his friendship with Lily under strain. After leaving school he joined the Death Eaters along with a large group of his fellow Slytherins.
After Lily Evans was killed by Lord Voldemort, Snape changed sides and became a member of the Order of the Phoenix, and double agent during the Second Wizarding War. With tremendous difficulty, he was able to prevent Lord Voldemort from learning the truth about Severus's true loyalty. Despite the opinons of most others, Albus Dumbledore trusted Severus for reasons no one could seem to figure out. Those reasons would eventually be revealed to be Severus's deep love for Lily Evans. Dumbledore also planned his own death with Snape. After Lord Voldemort's control of Hogwarts, Severus promised Dumbledore that, after his death, he would protect the students at Hogwarts. Snape participated at the Battle of Hogwarts, and was killed by Lord Voldemort, because Snape was thought to be the master of the Elder Wand. Severus Snape's portrait still remains at Hogwarts.