Professor Severus Snape (9 January, 1960 – 2 May, 1998) was Headmaster of Hogwarts and the former Potions-Master at Hogwarts. He was the Head of Slytherin and hated Gryffindors. His most common enemies when he was at Hogwarts at a young age were the Marauders (James Potter, Sirius Black, Peter Petrigrew and Remus Lupin). He named himself the Half-Blood Prince when he began his N.E.W.T.s after finishing OWLs and he edited a Potions book that his Potions teacher, Horace Slughorn, gave him. He put his self-made spells in the margin such as Levicorpus, Sectumsempra and Vulnera Sanentour, which is the cure for the second spell. Soon the Levicorpus spell slipped and Snape didn't catch it; now nearly the entire school knows Levicorpus, not just Harry and Snape. Near the end of the school year, Harry Potter obtained Snape's Potions Book and used Sectumsempra on Draco Malfoy. Snape instantly knew that Harry had his book after the accidental attack. Snape was then revealed to be the Half-Blood Prince to Harry, who was incredibly shocked that the man he hated had basically helped him throughout the school years.
He was in love with Lily Evans, and he sacrifised his life for her. After Lily's death, he felt it was his duty to keep her son, Harry, safe, and so became a spy to the light. He risked his life everyday until the final battle. He did not fight for his life. He died for love.
Harry Potter found out about his loyalty, and that Snape had been protecting him all this time. For this, he named his son Albus Severus Potter.
"The bravest man I've ever known."- Harry J. Potter.