By this point, Credence was slowly dying as his Obscurial nature poisoned him, the real reason that his phoenix had come to him, something that Dumbledore had recognised after having seen something similar with his sister Ariana, who was also an Obscurial.
As he had previously believed Credence could have been saved had he been given enough love, this indicated that at its earliest stages, it would have been possible for the power of love to cure them of their obscurus, but at a certain stage, a wizard/witch with an obscurus will no longer be able to be saved.
After defeating Credence, Dumbledore tells him that Grindelwald lied and that he did not abandon Credence, and the two part ways without further incident. By this time, Credence's Obscurus is slowly killing him, although he appears unaware of this fact.
His mother is killed, and as a result Aberforth is unable to care for his son. Credence is taken to America and put up for adoption, a fact known to no one but Leta Lestrange (Zoe Kravitz).
Credence's costume and hair change are so similar to Severus Snape's that it foreshadows his path in Fantastic Beasts 3 — consequently ruining his ending. Grindelwald abused Credence's need for an identity, telling him whatever he wanted to hear to secure his loyalty in his war against Dumbledore.
FANTASTIC BEASTS 3: WHAT HAPPENED TO CREDENCE AT THE END OF SECRETS OF DUMBLEDORE
Is Credence Tom Riddle's dad?
Voldemort was Tom Riddle and Dumbledore met Tom as a child. Riddle also attended Hogwarts. Riddle was also a Jr to his father, Tom Riddle Sr. Nothing lines up with Credence being Tom.
As she prepared to beat him yet again, Credence's Obscurus burst free. The dark force killed Mary Lou and Chastity, also causing heavy damage to the house.
Since Harry doesn't know Aberforth had a son and Albus doesn't find it relevant for Harry in the context of the Second Wizarding War, it makes sense neither brother mentions Credence in the Harry Potter series.
Aberforth met Credence's mother the same summer that Albus and Grindelwald met. Now, while living as part of Grindelwald's followers, Credence began to write messages to Aberforth through a mirror because he was desperate to come home – though to begin with, he didn't know he was writing to his father.
Nagini (d. 2 May 1998) was a Maledictus cursed to transform into a snake. Originating possibly in Indonesia, by 1927 she was a performer at the Circus Arcanus where she met Credence Barebone (Aurelius Dumbledore) and had a romantic relationship with him.
Quentin Kowalski may be a descendant of Jacob and Queenie Goldstein, though this would breach Rappaport's Law. Queenie and Jacob would need to have left the United States of America to marry as to protect Queenie from prosecution.
Without everyone's knowledge, except Newt, Credence survived, because Obscurial can't be killed while being in his Obscurus form. Barebone as a single shred fled away from the subway station to the destroyed Second Salem Church. When all shreds of his Obscurus connected together, Credence returned to his human form.
Although Aunt Petunia and Uncle Vernon were horrible to Harry, especially when he showed any resemblance to magic, the young wizard wasn't aware that he was magical. Harry's ignorance protected him from developing an Obscurus because he didn't develop a shameful attachment to his magic.
Using his disguise as Graves, Grindelwald came into regular contact with Credence Barebone. He believed Credence to be connected to the Obscurial due to a vision he received. Believing Credence was an orphaned Squib, Grindelwald emotionally manipulated him into helping him find the Obscurial.
Mary Lou was the leader of a group that preached hatred of the magical community to fellow No-Majs (non-magical people). Because of this internalized hatred — as well as physical and emotional abuse from Mary Lou — Credence repressed his powers and became an Obscurial.
Fantastic Beasts: The Secrets of Dumbledore confirmed that Credence Barebone/Aurelius Dumbledore (Ezra Miller) is the new Snape (Alan Rickman) through a very familiar line delivered by Aberforth Dumbledore (Richard Coyle). Fantastic Beasts 3 finally shed light on the Credence being Aurelius Dumbledore plot twist.
Grindelwald had claimed the phoenix's presence around Credence proved he was a Dumbledore, but it seems he was telling a half-truth, because in reality the phoenix kept returning to Credence because they are drawn to provide strength and comfort for those who are dying.
Fantastic Beasts: The Secrets of Dumbledore finally revealed that Credence (Ezra Miller) is Aberforth Dumbledore's (Richard Coyle) long-lost son, but his mother could very well be a Gaunt, making Credence related to Voldemort (Ralph Fiennes).
Leta had become the fiancée of Newt's older brother Theseus by 1927. In that same year, she sacrificed herself for them during a rally held in Paris by Gellert Grindelwald by distracting him by destroying his skull-hookah with a powerful spell. Grindelwald's flames then engulfed Leta, incinerating her.
The boys tried to get Ariana to show them her trick, but when she was unable to because of her young age, they turned violent and started to attack her to stop her from using magic. As a result of the attack, she became traumatised to the point of her unwillingness to use magic, causing her to develop an obscurus.
Mary Lou Barebone (played by Samantha Morton) is a fanatical No-Maj campaigner against wizardry and the abusive, adoptive mother of Credence, Chastity, and Modesty.
Dumbledore tells Newt Scamander (Eddie Redmayne) that in 1899, during the same summer that Albus fell in love with Grindelwald, Aberforth also fell in love with a woman from Godric's Hollow. They had a baby boy together, but the woman was sent away before she gave birth, and Aberforth never got to be a father.
Fantastic Beasts 3 reveals that Credence is Aberforth Dumbledore's illegitimate son. Since Grindelwald was telling Credence the truth about his name being Aurelius Dumbledore, it seemed logical that he's one of Albus Dumbledore's siblings.
Although Aberforth was a brother of Albus, he did not study the art of magic as much as Albus did. He cared more for the Dumbledore family than Albus did and abandoned his studies to help them out. He was powerful, but not quite as powerful as Albus.
