In the
Harry Potter stories by
J.K. Rowling, this is the teaching post that seems cursed. Every year there's a new
teacher, as previous ones succumb to various catastrophes. Of course if they were really good at
defence against
dark arts, this shouldn't happen. But often the flaws are within the characters, not the evil forces they have to contend with. The one teacher who we suspect might be really good at it,
Severus Snape, has not yet been given the job, and often appears highly
resentful of this fact.
Anti-SPOILER Charm needed now...
In Harry's first year (Harry Potter and the Philosopher's Stone) the teacher is Professor Quirrell, a nervous stuttering wreck in a turban, who suffers under the small disadvantage of having the earthly hulk of the Dark Lord Voldemort fused to the back of his head. From the very beginning he seems scared of what he has to teach, as if from live encounters with evil creatures. The DADA lessons are hardly mentioned in the course of this book, and we don't hear much of what the dark arts are or what the defences are against them.
In second year (Harry Potter and the Chamber of Secrets) it is Professor Gilderoy Lockhart, a camp narcissist whose incompetence is only equalled by his desire to project an aura of invincible competence. His lessons are boastful re-enactments of his adventures defeating evil semi-intelligent humanoids such as ghouls, vampires, werewolves, and banshees; none of which actually happened as he said, so it's doubtful how much value the lessons hold. The students all hate them. He loses his memory at the crucial moment, and makes a cameo appearance in a later book in a therapeutic ward for the incurably fey.
In third year (Harry Potter and the Prisoner of Azkaban) it is Professor Remus Lupin, a frazzled, kindly man whom the children take to immediately (except the Slytherins, of course), but who also suffers from an interesting personality problem, being a werewolf, and therefore in theory one of the dark beings he should be protecting the students from. He makes a good teacher, but as his secret comes out at the end he is obliged to pack his meagre bags and make his way hobo-like into the world again. Many in the fan network hope he will come back to the job in a future book.
For the first time they are taught useful Defences Against the Dark Acts, because Lupin brings in real creatures to practise on: small, nasty imps of various kind, such as kappas and a boggart. This is the opportunity for a very important development in Harry's career, as the boggart assumes the form of whatever a person fears most, and in Harry's case that is the Dementors, merciless fear-inducing guards of the wizard prison Azkaban. To counter them Lupin privately tutors Harry in conjuring up a Patronus, a powerful spectre created by happy thoughts; and this advanced spell is highly useful to Harry in several later emergencies.
In fourth year (Harry Potter and the Goblet of Fire) it is Mad-Eye Moody, a crazed-looking veteran of numerous highly dangerous battles with the Dark Arts, with pieces missing. If anyone can teach them how to survive such attacks, it is him. Sadly, he spends the entire year confined to a small box in drugged sleep. The teacher is a fake Moody who has the real one prisoner.
Nevertheless the impostor, to act the part of the well-known Moody and also for sinister private reasons, does a good job of teaching them. He, with Headmaster Dumbledore's permission, and against Ministry of Magic rules, considers them old enough to know about the worst that dark wizards can throw at them: the three Unforgivable Curses. Use of any of these against a human being entails life imprisonment in Azkaban. The Imperius curse was how Lord Voldemort enslaved many to his will. The Cruciatus curse was how his supporters tortured Neville Longbottom's parents into madness. And Voldemort killed Harry's parents with Avada Kedavra, the only known survivor ever of which is Harry himself. Later in the book the rearisen Voldemort in person uses all three of these against Harry Potter.
In fifth year (Harry Potter and the Order of the Phoenix) we have an interesting split between the teacher of Defence Against the Dark Arts, and the one actually teaching them Defence Against the Dark Arts. Due to the interesting goings-on at the end of the previous year, Hogwarts School is now under a kind of martial law imposed by the Ministry of Magic, and the gross and vile civil servant Dolores Umbridge has been parachuted in as High Inquisitor to make sure signs of independence are stamped out. She teaches Defence from a ministry textbook, without regard to the real conditions prevailing: the Ministry are in a state of denial about the return of Lord Voldemort.
So Hermione proposes a bold plan: there is one wizard who has both brilliant natural talent and real experience in defeating terrible forces, and who is therefore uniquely placed to give willing students secret lessons: Harry Potter himself. They form a clandestine society called Dumbledore's Army, and Harry begins equipping his compeers with what they'll need to know in the upcoming war against the Dark Lord
EXTRA-STRENGTH Anti-SPOILER Charm needed now...
In sixth year (Harry Potter and the Half-Blood Prince) Snape gets his dearest wish, the DADA job...