Fantastic Beasts: The Secrets of Dumbledore

The second film ends with the expulsion of Gellert Grindelwald from Paris, which cost Newt Scamander the loss of Credence Burbone and the death of many agents of MACOSA (US Magic Congress). However, thanks to the fight with Grindelwald, Newt manages to steal a bubble of blood from him - a symbol of the oath that did not allow Albus Dumbledore and Grindelwald to fight against each other and pass it to Albus.

At this point, Grindelwald gives Credence a magic wand, and makes a crow, a symbol of the genus Lestrange, Phoenix, and informs the latter that this bird always came to the rescue at the right time to all members of the genus to which the pinworm belongs. Grindelwald reveals the real name of the obscura: Aurelius Dumbledore.