Notes

D.A.D.A Grade 1 task by Sehun (1st AU, Slytherin)
1. Quirinus Quirrell (1991-1992)
Before teaching D.A.D.A., he went out in search of Lord Voldemort, in hope of achieving recognition for finding him. However, after Voldemort knew that Quirrell taught at Hogwarts, he took over his body to continue the struggle to murder Harry Potter.
During his study, he most likely obtained a high-geaded OWL and NEWT in Muggle Studies and D.A.D.A. He was noted to have had a gift for the theory of Defensive Magic. However, he developed a theoretical interest in the Dark Arts. He was hailed as a good teacher by Ministry of Magic standards.
2. Gilderoy Lockhart (1992-1993)
He was a half-blood wizard and a famous wizarding celebrity who authored many books on dark creatures. He received many awards for his supposedly great deeds, and was invited to join the Dark Force Defence League as an honorary member.
Lockhart was the only willing applicant for the current position and he became professor of D.A.D.A class. His classroom and office at Hogwarts were decorated with pictures and portraits of himself. He also decorated the office with copies of his publication. Of the three professors I describe in this essay, he was the only one having no direct relationship with Lord Voldermort.
3. Severus Snape (1996-1997)
He was a half-blood wizard, just like Lockhart. He was also a member of the Order of the Phoenix and played a very important role in both of the Wizarding Wars against Lord Voldemort. Although he appeared to have negative aura, he is actually my favorite D.A.D.A. professor aside of Professor Lupin.
In his early years working at Hogwarts, he was assigned to teach Potion classes. He was a strict teacher with a very little tolerance in terms of disciplinary. He followed Lord Voldemort on attempt to kill him for he killed his forever love, Lily Potter née Evans, Harry's mother. He then became a D.A.D.A. professor to protect Hogwarts, including Harry.