The only known counter-spell is sacrificial protection. However, one may dodge the green bolt or block it with a physical barrier or object. The Killing Curse, as an "unblockable" Curse, cannot be intercepted by another spell, except in circumstances of Priori Incantatem, where the caster and his opponent's wands and spells are locked together. An explosion or green fire may result if the spell hits something other than a living target.
Only two wizards are known to have survived blows from this deadly curse: Harry Potter and Tom Riddle.
The Killing Curse was invented during the early middle ages, by Dark witches or wizards. The curse was created primarily as a means of quickly and efficiently slaying one's opponent in a duel.
Along with the Cruciatus and Imperius curses, the Killing Curse is known as one of the most terrible curses in the wizarding world. After the Wizards' Council was reformed into the Ministry of Magic tighter restrictions were placed on the use of certain kinds of magic. The Killing Curse was deemed by the Ministry to be Dark magic, and, along with the Cruciatus and Imperius curses, were declared "unforgivable" in 1717, with the Killing Curse considered to be the most deadly of the three. Cursing another human with the Killing Curse would carry the punishment of a life sentence in Azkaban.
However, the First Wizarding War, when Barty Crouch Sr. was in charge of the Department of Magical Law Enforcement, he fought violence with violence, legalising the three Unforgivable Curses for Aurors against the Death Eaters in order to win the war. This was repealed once the war was over as it was no longer necessary. When Lord Voldemort took over the Ministry, the three curses were once again legalised: this time every wizard and witch had the right to use them as they please. In fact, they were practiced in Hogwarts as part of the curriculum of Dark Arts class under the tutelage of Professor Amycus Carrow. After Voldemort's death and the revolutionising of the Ministry under Minister Kingsley Shacklebolt, the three curses were once again forbidden.
It should be noted that despite the curse being illegal, references have been made to Aurors using deadly force against opponents, though whether this means they were authorized to use the killing curse specifically is unclear. Despite the circumstances, it is unknown whether the Killing Curse was used by anyone but Voldemort and his Death Eaters during the Battle of Hogwarts. It is also known that use of this curse may go unpunished if there is sufficient evidence that the caster did so under the influence of the Imperius Curse.
The Avada Kedavra curse is recognisable by the flash of green light and the rushing noise emitted from the caster's wand. When the curse hits a living, organic target it invariably kills them without injury. However, when this curse hits an inanimate target the effect varies: it can produce small fires, small greenish explosions, or explosions of such intensity that can blow up an entire story of a cottage. It is known by most wizards as Lord Voldemort's signature spell. Presumable, it kills it's target by tearing the victim's soul from their body. However, certain objects, such as statues manage to block the curse without any visible damage to itself. It should be noted that curse did not terminate the animation of (i.e. "kill") the statue, however, the statue was only animated by magic and so presumably had no real life in him for the curse to take away.
The curse requires a great deal of magical talent to perform correctly. It is claimed that if an untrained student performed it on another at one time, that person would probably get nothing more than a nosebleed. It is possible to cast the curse non-verbally, Lord Voldemort could cast it non-verbally. However, the lack of the incantation may have been for suspense. Whether this is true or not is unknown. Large amounts of concentration is likely required to cast the Killing Curse, which is probably why Death Eaters don't use it as their primary offensive spell.
The Killing Curse is described as a jet or flash of blinding green light that "illuminates every corner of the room" followed by a rushing sound, which causes the victim instant death. Victims of the Killing Curse are identified by the fact that they simply appear to have dropped dead for no biological reason. Indeed, victims seem "perfectly healthy" apart from the fact that they are dead. This lack of visible injuries is one that had confused Muggles throughout the years of its use, requiring many Ministry of Magic officials to modify memories.
Presumably, the Killing Curse does not inflict any pain on its target, since it causes instantaneous death.
The Killing Curse can be dodged or physically blocked by an object, such as the statues Dumbledore animated to protect Harry Potter during his duel with Lord Voldemort after the Battle of the Department of Mysteries. The Killing Curse is known to be unblockable, as once it strikes the living victim, it almost always results in immediate death. There is "no counter-curse" since it is not possible to revive the dead. However there are some exceptions:
The most effective method of surviving the Killing Curse is through Sacrificial Protection. The sacrifice of one's life for another, a manifestation of the powerful magic of love, is the most potent defense against the "unblockable" Killing Curse. Harry Potter, was saved by his mother, Lily Evans, lovingly sacrificed herself when she shielded her son with her body, making him the first known survivor of this Curse. Harry Potter was the only person known to have survived Avada Kedavra with no ill effects, aside from attaining a scar.
Another defense employed against the Killing Curse is the creation of at least one Horcrux. The creation of Horcruxes is a preventive measure, created by a wizard long before he faces an actual Killing Curse attack. However, this is less effective than Sacrificial Protection, since it only allows a little more than the soul of the target to live, while the target's body still dies. If one has Horcruxes, they will not be dead, but they will barely be alive and will be reduced, as Voldemort was when the Killing Curse backfired with his attempt to kill Harry Potter in 1981. Voldemort's Horcruxes tethered his soul to life.
The Curse drove his mangled soul from his body and split his unstable soul, leaving him to roam only as a shadowy spirit, unable to move on to death but in a less-than-alive life form. If possible, one can make a Regeneration potion to came back to life, but it requires the bone of the father, the flesh of the servant, and the blood of an enemy. Upon the destruction of all his Horcruxes, Voldemort had no more defence against death, and was finally killed by his own deflected Killing Curse.
Phoenixes are semi-protected from the Killing Curse, due to them being immortal. When hit by the curse, they still "die" bursting into flames. However, they then are reborn from their ashes.
Blocking the CurseEdit
The Priori Incantatem effect is when two wands that share the same cores are put into battle against each other. One wand will then force the other wand to repeat its previously-cast spells. Because of this, an Avada Kedavra Curse can be blocked if a wand that shares the killer's wand's core fires a spell at it: both spells will connect and thus the wizard has been spared by the Killing Curse. However, since wands with twin cores are extremely rare, this method cannot be employed "at will".
Priori Incantatem once occurred in a duel between Harry Potter and Lord Voldemort in the graveyard during Harry Potter's fourth year. Voldemort cast the Killing Curse and Harry cast the Disarming Charm, and because their wands had twin cores, Priori Incantantem occurred; Harry was not killed and was able to hold Voldemort off to give him time to escape.
The spell can be directly countered using a Stunning Spell, in which case red and green jets of light will meet and create multi-coloured sparks. Since neither spell is able to reach its intended target, neither will have any effect.
Other Targets and DodgingEdit
If another target is placed between the caster and the targeted individual, then the new target will take the hit of the Killing Curse, which may simply result in an object being destroyed or damaged. One can also avoid the effects simply by dodging or if the caster has poor aim, as with many attacking curses of this type, the spell must be directly targeted at the intended victim.
- Harry survived two direct attacks: once in 1981 after his mother's self-sacrificing love protected him from Lord Voldemort, and once in 1998 after the curse, cast again by Voldemort, failed to kill Harry, as he was tethered to life by Voldemort himself, due to Lily's blood protection which he took inside himself during his rebirth.
- Lord Voldemort remained alive after the aforementioned curse from 1981 rebounded and struck him because of his Horcruxes. Voldemort was notorious for using this curse regularly and indiscriminately.