Directed by: David Yates
Starring: Colin Farrell, Ron Perlman, Eddie Redmayne, Ezra Miller
Genres: Adventure, Family, Fantasy, Harry Potter
Newt Scamander: My philosophy is if you worry, you suffer twice.
Queenie: She's a taker, you need a giver.
Jacob Kowalski: I don't think I'm dreaming.
Newt Scamander: What gave it away?
Jacob Kowalski: I ain't got the brains to make this up.
Mary Lou: Are you a seeker, a seeker of truth?
Newt Scamander: More of a chaser.
Factual error: In opening scene of of 1920s New York the Statue of Liberty is in view with the modern refurbished gold leaf torch, not the original iron and glass torch. Lady Liberty's torch was not replaced until October 8th, 1984.
Trivia: Because so little architecture from the decade still exists, David Yates chose not to shoot on location; instead, the production designers created, from scratch, their own painstakingly detailed version of 1920s New York as a practical, physical set.
Question: Why does Graves want to find an Obscurial so badly?
Answer: In the second film in this series, Crimes of Grindelwald, it's revealed that Grindelwald had a vision years ago that he would use an Obscurial to aid him in killing Dumbledore, since the two of them were magically barred from fighting each other. That's why he was so determined to sway Credence to his side.
Chosen answer: Obscurials often manifest around childhood. Children are young and influential, so Graves/Grindelwald can persuade one to let their magic free without much protest in a public place as an indestructible weapon. As we witnessed when Credence rampaged through New York, Obscurials would be far more destructive to whole cities than just casting a lot of spells.
There's WAY more to it than that-although you'd never know it if you only ever watched the original HP films and never read the books. In short, Graves/Grindelwald has had first-hand experience with an Obscurial before. Remember that painting Aberforth Dumbledore had on the wall of the Hog's Head Pub in Deathly Hallows Part 2? That was Ariana Dumbledore, his and Albus' sister. When she was a child, she was attacked by three Muggle boys who caught her doing magic, which traumatized her and caused her to become an Obscurial; the Obscurus inside her later killed the siblings' mother. At the same time, Dumbledore and Grindelwald were plotting together to bring wizards out of hiding and reassert their superiority over Muggles with the help of the Elder Wand. In the end, Aberforth confronted them, leading to a chaotic duel that resulted in Ariana being killed by a stray curse. Dumbledore and Grindelwald went their separate ways, with Grindelwald putting their visions of wizard supremacy into action, while Dumbledore's grief for his sister led him to repent and shun power for the rest of his life. Virtually none of this made it into the movies. But that's why Grindelwald wanted an Obscurial so badly-because he'd seen one before and knew first-hand how lethal they could be.
Actually, it was never 100% confirmed that Ariana did become an Obscurial.