Erroneously believing Snape is the master of the Elder Wand and that Snape's death will make him the master of the Wand, Voldemort kills Snape by having his pet snake Nagini bite him through the neck.
The great serpent bit him in the neck, and injecting him with the venom, preventing it from healing (even by magical means), thus leading to Snape's demise.
Why did Voldemort asked Nagini to kill Snape? Theory: Voldemort thought that Snape was the master of the Elder Wand because he (Snape) killed Dumbledore and it would backfire at him and kill him (Voldemort) instead so he ordered Nagini BUT he did not know Harry was the master of the Elder Wand so he used Avada Kedavra.
In 1994, Death Eaters Peter Pettigrew milked the venom from Nagini's fangs and used it, along with unicorn blood, to concoct a dark potion, which allowed Voldemort's shattered soul to regain a rudimentary, but physical form.
Snape tried to reason with Voldemort, but Voldemort instead moved Nagini in her orb over Snape, commanding Nagini to kill Snape, in which she bit into Snape's neck with her poisonous venom. Voldemort then left Snape to die, taking Nagini with him.
The Story of Nagini (+ How She Met Voldemort) - Harry Potter Explained
Why didn't Snape defend himself against Nagini?
He could not do so openly, because she was in a magical cage to protect her from harm. Despite the fact that Snape is a talented wizard, he took too long to protect himself – because he was not even attempting a defensive spell. He was collecting his strength to attack Nagini in her cage.
Voldemort had to kill Snape because he needed the wand's allegiance to switch. Voldemort knew he couldn't cast Avada Kedavra with the Elder Wand to kill its master, so he ordered Nagini to be the one who killed Snape.
Delphini was born in secret at Malfoy Manor in early March 1998 as the result of a liaison between Bellatrix Lestrange and Lord Voldemort. On 2 May 1998, both of her biological parents were killed in the Battle of Hogwarts.
Voldemort had a special relationship with Nagini, as she was his pet and one of his Horcruxes. According to Dumbledore, Voldemort had strong feelings for Nagini that he had not for anyone else; she was the one living thing that he had ever cared about.
Assuming it is the case, evil nature of Nagini's snake half who later joined Voldemort is easily attributed to the loss of humanity which ended up in her human half reminiscent to Urizen who bereft of his true self Vergil's humanity which ended up in his other half V.
Nagini, Voldemort's snake, then eats Professor Burbage's dead body. A story about her "resignation" from Hogwarts appears in the Prophet, but members of the Order of the Phoenix discount it, as they are unable to locate her anywhere after that. Burbage is later replaced as Muggle Studies teacher by Alecto Carrow.
At this point, McGonagall begins to gain the upper hand as it becomes clear he cannot further transfigure or counter her attack, so the only way he avoids it is by taking refuge behind a suit of armour that he forces in front of him.
The Disarming Charm became Harry Potter's signature spell, and it notably caused the final defeat of Lord Voldemort during the Battle of Hogwarts by rebounding his Killing Curse, because the Elder Wand recognised Harry as its master through the spell connection, and thus strengthened the Disarming Charm to the point ...
It is presumed that Voldemort and Nagini met in the forests of Albania or perhaps a little earlier and went there together. Either way, Nagini allowed Voldemort to possess her occasionally, as fans theorize, to have a physical connection to the Wizarding World.
Behind the scenes. When Harry and Hermione are on the first floor of Bathilda's house, Nagini (inside the corpse of Bathilda) tells Harry to 'Come! ' from the next room in Parseltongue. In reaction, Hermione jumps and clutches Harry's arm, and the two of them obey the command.
Before her death, Bellatrix secretly gave birth to an illegitimate daughter named Delphini, whom she conceived with her beloved master, Lord Voldemort. Delphini was conceived sometime after the Battle of the Department of Mysteries in 1996 and before the Skirmish at Malfoy Manor in 1998.
Unknown to nearly all, it would be revealed years later after their death that Bellatrix and Voldemort had in fact engaged in a sexual relationship, resulting in the birth of their daughter, Delphini, who years later threatened to upset the timeline to be with her father.
As Bellatrix and Voldemort were both killed in the Battle and Bellatrix's husband Rodolphus was imprisoned at Azkaban, Delphi was raised by Euphemia Rowle, a Death Eater. However, the life at Euphemia's was miserable for Delphi as Rowle did not really care for her and only took her in because she was paid for it.
In the play "Harry Potter and the Cursed Child," which has become part of "Harry Potter" canon, it was revealed that Bellatrix conceived a child with none other than Lord Voldemort.
Delphini Diggory was a mysterious young woman, whose past was filled with mystery. When she first met Albus and Scorpius, she claimed to be Amos Diggory's niece and accompanied the boys as they travelled back in time in an attempt to change the course of time and save Cedric Diggory.
Malfoy spots Harry and casts a Cruciatus curse; Harry, defending himself, using the Half-Blood Prince's Sectumsempra spell without knowing its effects. To his horror, it gashes Draco's face and chest, spilling his blood everywhere. Moaning Myrtle flies off, screaming.
Why did Harry's scar hurt when Snape looked at him?
J. K. Rowling stated that the pain from Harry's scar on his forehead was caused by the piece of Voldemort's soul trying to leave his body through the wound it entered to rejoin its master's soul.
