Sirius was arrested, accused of murdering Pettigrew and the muggles and of serving Voldemort, and was promptly thrown in prison by Barty Crouch, Sr. without receiving a trial. He spent the next twelve years in Azkaban, brooding over his friends' deaths and obsessing over Pettigrew's betrayal.
Peter Pettigrew, the Secret Keeper for the Potter family who betrayed them to Voldemort. Sirius Black was originally meant to be the secret keeper for James and Lily Potter, but Sirius thought Voldemort was on to him (he thought that Remus Lupin was a spy), therefore passing on the Secret Keeper to Peter Pettigrew.
Sirius Black is introduced in the third Harry Potter installment as the Prisoner of Azkaban, a dark and menacing figure feared by the Wizarding World almost as much as Voldemort himself. Everyone believes he's a mass murderer who betrayed Harry Potter's parents to the Dark Side.
Dumbledore's lack of belief that Sirius is innocent is also suspect. Sirius was a member of the Order of the Phoenix which fought against Death Eaters, but Sirius also was as close to James as a brother, the Potters even took him in when he ran away from home.
During The Purity War, Sirius Black was a member of The Order of The Phoenix and gave a confession to being a member of The Death Eaters, and betraying the Potters to The Dark Lady, admitting to putting the Imperius Curse on dozens of other Death Eaters. For his crimes, he was sentenced to Life in Azkaban Prison.
Why Dumbledore WANTED Sirius to ROT in Azkaban - Harry Potter Theory
Did Snape know that Sirius was innocent?
No, he didn't know. That's why Rowling specified that in Vold War One the Death Eaters were organised into cells, with each only knowing the identity of a few of the others. So Snape didn't know Pettigrew was a Death Eater, and he didn't know that Sirius wasn't one.
The Order battles the Death Eaters in the "Death Chamber". During a frenzied duel with Bellatrix, Sirius taunts her for failing to harm him. Bellatrix strikes Sirius with a curse, sending him backwards into the veil and to his death.
When questioned by Bellatrix about his loyalties, Snape says he has been working for Voldemort ever since Voldemort's return, and explains his actions in the previous books in that light. He points out that gaining Dumbledore's trust and protection has kept him out of Azkaban and free to operate on Voldemort's behalf.
His help at the Ministry of Magic might result in a smoother mission. Thanks for A2A. No. Sirius had no idea that Harry was a Horcrux, and I think that is one of the kindest things that was done.
Dumbledore didn't know that Sirius was innocent. He knew there was a spy within the Order of the Phoenix and after Snape passed along the prophecy to Voldemort he knew that there was a danger to the Potters. He also knew there as a danger to the Longbottoms as well since Neville fit the details of the prophecy too.
For using the Unforgivable Cruciatus Curse to torture the Longbottoms until they went insane, Bellatrix and her three associates were sentenced to life imprisonment in Azkaban. At her trial, Bellatrix proudly and defiantly proclaimed that Voldemort would rise again.
The silver hand Lord Voldemort had given Pettigrew interpreted his hesitation as weakness and/or disloyalty, and strangled him to death, saving Harry and finally finding redemption for his treason, despite his reputation remained tarnished as many remained dubious of the evidence of his innate bravery.
Sirius also disliked Regulus because of his ambition to become a Death Eater, but he was unaware that Regulus later attempted to destroy one of Voldemort's Horcruxes. Sirius regretted how young his brother died and wished Regulus hadn't been as soft to go with what their parents told him to do.
In fact, James outright tells Lily that he's bullying Severus Snape because of the “fact that he exists, if you know what I mean”. James Potter saved Severus Snape from the werewolf prank before the Snape's Worst Memory scene happened. The mastermind of said prank is Sirius Black, James' best friend.
Summary. Peter Pettigrew's betrayal of the Potters and allegiance to Voldemort was a result of his unhealthy admiration for James and desire for power. Sirius Black was believed to be the Potters' Secret Keeper, but he secretly switched with Peter Pettigrew, who turned out to be a mole.
Sirius's intense love for James, his grief after James's death, and his anger towards Peter drove him to insanity, getting him locked up in Azkaban for crimes he never committed.
Notably, Voldemort appeared to be entirely unaware of this split, as he later created a seventh Horcrux in his quest to have six, and continued to target Harry Potter despite him now holding part of Voldemort's own soul.
Draco, who implies that he is aware of how Sirius Black was supposedly involved in the deaths of Harry's parents, also taunts Harry about the impending threat of Black: "If it was me, I'd want revenge. I'd hunt him down myself."
The clue he received in the film was from Bellatrix, who was in a frantic frenzy when she thought her vault was broken into. He is ultimately able to identify the cup as a Horcrux because of his ability to hear the piece of Voldemort's soul contained within them, an ability which is not present in the books.
Severus Snape's nickname, the Half-Blood Prince, was a clever description of his half-blood lineage. Snape chose the name as a tribute to his mother and to distance himself from his muggle father, drawing an interesting parallel between this character and Lord Voldemort.
Severus Snape earned the moniker "Half-Blood Prince" during his time at Hogwarts, owing to his mixed magical heritage as the child of a pure-blood witch named Eileen Prince and a Muggle father named Tobias Snape.
He hid them using the only thing that would work against Voldemort. He used Fidelius charm and after that even secret keeper was to be protected using that as Sirius said in PoA. The plan failed because wormtail who was their secret keeper betrayed them.
During the final battle, Bellatrix was the last Death Eater standing. She was eventually killed in a duel by Molly Weasley after her attempted murder of Ginny Weasley. Before her death, Bellatrix secretly gave birth to an illegitimate daughter named Delphini, whom she conceived with her beloved master, Lord Voldemort.
Remus fought at the Battle of Hogwarts on 2 May 1998, during which his wife was murdered by Bellatrix Lestrange. Remus was also murdered by Death Eater Antonin Dolohov, during the first half of the same battle. His death was possibly avenged by Filius Flitwick.
