How Does Dumbledore Break The Blood Oath?
Dumbledore reveals early in the movie that Newt has to move against Grindelwald because he can't, but it's only later we come to know why: the pair made a blood pact, meaning they cannot fight each other. Except, of course, that is what they end up doing in their famous duel in 1945, the event the Fantastic Beasts franchise is gradually building up to.
That means the blood oath needs to be broken, but given how little we really know of this kind of magic - the closest approximation is the Unbreakable Vow, which, well, can't be broken - it's unclear just how that's going to happen.
Does Grindelwald Work With Or Against Hitler?
While we know that Grindelwald wants to rule over Muggles, the movie finds him trying a slightly different marketing tactic. It still fits with the 'greater good' we've come to associate with him, but he presents the human wars to come, and the wizard lives that will be lost too, as reason to stand with him in his drive to create a new world order.
World War II imagery factors heavily into this, and since the series will overlap with the conflict, it's going to be hard for it to ignore. Grindelwald, like Voldemort before him, has already been used as a pseudo-Hitler, so does that mean he'll actually work with him during WW2? Or, since Hitler was still a Muggle, will he actually work against him 'for the greater good'?
Who Does The Prophecy Refer To?
A son cruelly banished. Despair of the daughter. Return, great avenger. With wings from the water.
Harry Potter has a long history with prophecies, and now there's a new one to throw into the mix, courtesy of The Crimes of Grindelwald and Tycho Dodonus, who made it. But what does it mean, and to whom does it refer?
The first reading is that the son is Corvus Lestrange, who is rumored to be alive (and be Credence), with Leta being the despairing daughter. Yusuf Kama believes himself to be the 'great avenger', hence his Unbreakable Vow. And the wings from the water refers to the boat ride that killed Corvus.
But, of course, Credence ISN'T Corvus. Instead, he's Aurelius Dumbledore, which changes how we see the entire prophecy. If we then take it that the 'son cruelly banished' is Aurelius, who was sent to America for reasons unknown and kept hidden, then it becomes about his return - he's back to discover who his family is, and now to take down his brother, i.e. 'great avenger' - with the despairing daughter being Ariana, and the wings of the water being both the boat and sea, but also, perhaps, how his Obscurus moves.
Even that might be too simple though. This is the Wizarding World, after all, where prophecies aren't always as they seem. Instead of avenging Albus Dumbledore, then, could it mean Credence/Aurelius will ultimately play a part in Grindelwald's defeat? Or is there another reading to the prophecy?
Is The Phoenix Really Fawkes?
While we already knew that Albus Dumbledore had a special connection to phoenixes, through both Fawkes and his Patronus, The Crimes of Grindelwald expands that to encompass the entire family, establishing a mythical link between them and the creatures, who'll appear in their time of need.
This is then used as a means of hammering home the point that Credence actually is Aurelius, with a phoenix bursting forth right at the very end. This could just be any old phoenix, of course, but might it really be Fawkes? We don't yet know how Albus came to possess the creature, only that they have a serious bond. Did Fawkes appear to Aurelius first then, before transferring his allegiance to Albus, either because he had a greater need, or after Aurelius' death?