The Unforgivable Curses are introduced in Harry's fourth year in the Goblet of Fire. It's during feigning Mad-Eye Moody's Defense Against the Dark Arts class that Harry sees first-hand the spell that killed his parents. The Killing Curse emits green light and instantly kills its target. The Cruciatus Curse inflicts pain, and the Imperious Curse works to control its victims.
Even these minute details seem to be swept over in the films, though. CGI and verbal explanation can only do so much to truly represent that malice these curses possess. There are even times in the wizarding world where the Dark wizards aren't the only ones using these illegal spells. In case you are feeling a bit neglected by these interesting facts, here are ten things about the Unforgivable Curses that the movies leave out.
10 Classified as Unforgivable in 1717
The harsh rules attached to using any of this curses dates back to the 18th century. These three spells became ostracized and banned for their use in 1717 after they were routinely put to sinister use. However, the ban for these curses lifted briefly during the First Wizarding War, and again during the Second Wizarding War under Voldemort's brief reign. Other than that, any utterance of these spells grants witches and wizards a lifetime sentence to Azkaban.
9 Harry Tried To Use One On Bellatrix
This scene is actually in the movie, but it's not made fully clear the intensity of this moment. Running through the Atrium in the Ministry of magic, Harry shoots a spell towards Bellatrix, which just barely misses her, but still causes her to fall to the ground. This is right after she kills Sirius Black, so Harry is out for blood. She turns and has a remarkable look of complete fear. It's clear that she is afraid of Harry at that moment because he had actually just tried to use the Cruciatus Curse on her.
8 Harry Uses Them A Lot In Year 7
During the trio's multiple infiltration heists, Harry uses the Imperious Curse. He uses it to sneak into Gringotts by putting two of its workers into a trance in order to sneak into Bellatrix's vault. At this point, Voldemort had legalized the use of the Unforgivable Curses. Harry later successfully uses the Cruciatus Curse on Amycus Carrow just before the beginning of the Battle of Hogwarts. There is no evidence of Harry or any of his friends every trying the Killing Curse, and eventually the Minister of Magic makes these spells illegal again.
7 What The Killing Curse Feels Like
The Killing Curse does not just simply kill the other person. Any incantation of Avada Kedavra is likely to hit its target, so upon hearing these words, wizards instantly recognize their defeat. There is no blocking this curse, nor is there a countercurse that can be used to rectify it. The result is instant death, though biologically, there is no telling what the spell does to the body. Voldemort survives his own curse after it recounters from his attempt to kill Harry as a baby. He believes that the Killing Curse rips the soul out of the body while simultaneously inflicting a "pain beyond pain."
6 What The Cruciatus Curse Feels Like
The effect of the Cruciatus Curse is a feeling of intense pain and agony that goes on as long as the wizard who conjured it lets it. It is used as a means of torture and is used regularly by Death Eaters in the first war. When Harry tries to inflict this curse on Bellatrix, she lets him know that, in order for it to work properly, he must truly hate them and enjoy the pain he is causing that individual. Harry feels the effects of this curse himself when Voldemort hits him with the spell after the final maze during the Triwizard Tournament. He describes the sensation as, "feeling like his head was being split open while having his bones set on fire."
5 Purpose Of The Imperious Curse
The Imperious Curse is the most docile of the Unforgivable Curse. It doesn't cause pain or any form of discomfort. However, it can make people inflict their own pain or even death. Viktor Krum is under the Imperious Curse during the Triwizard Tournament as a way to help Harry get to the cup, which is subsequently used a Portkey to Voldemort. This curse makes the recipient do the proverbial bidding of the caster, though one is able to fight this curse. Harry, in fact, became quite skilled at fighting off the effects of the Imperious Curse. Many Death Eaters, such as Lucious Malfoy, also used this spell as an excuse as to why they were "unwillingly" acting under Voldemort's commands.
4 Frank and Alice Longbottom's Story
Although Frank and Alice Longbottom, parents to Neville Longbottom, survive the Cruciatus Curse, the damage was severe. Under Bellatrix's wand, the two were subject to ruthless torture—so much so, that they ended up going insane from it. They now reside at St. Mungo's Hospital where Neville visits them on a regular basis. In the books, readers get to experience the scene where Neville interacts with his mother, who has the mindset of a child. The two former Aurors could do nothing to stop the pain, but it wasn't enough for them to die. This particular act against the Longbottoms is regarded as one of the more crude and despicable uses of the Cruciatus Curse to date.
3 Hermione Under The Cruciatus Curse
At Malfoy Manor, Bellatrix takes Hermione away in order to interrogate her. From the dungeons below, Harry and the rest of the imprisoners can hear Hermione's agonizing screams. However, in the films, it is made to believe that her pain comes from the "Mudblood" wound that Bellatrix carves into her arm. When in reality, Bellatrix was ruthlessly putting Hermione under the Cruciatus Curse in order to torture information out of her.
2 Fawkes Survived the Killing Curse
Voldemort and Harry are said to be the only known creatures to survive the Killing Curse. However, during the battle between Voldemort and Dumbledore in the Ministry of Magic, Fawkes comes to Dumbledore's aid. In his assistance, Fawkes takes a Killing Curse for his master and actually swallows it before falling to his death. This doesn't last long, though, as Fawke's nature has him reborn from his own ashes immediately after death.
1 Death Eaters Use Them At Hogwarts
Hogwarts is overrun by Death Eaters during Harry's absence in what would have been his seventh year at Hogwarts. They take over as professors and begin teaching students about the Unforgivable Curses, even using some of them on students as a form of instruction. They would also use these spells on students for punishment and would after make other students perform the curses on each other.