Fantastic Beasts 2 Ending And Twist EXPLAINED

6. Dumbledore Has The Blood Oath

The idea of a blood oath that literally takes little bubbles of blood and makes them dance and then live together inside a vial to remind the oath-swearers of their bond is a new thing to the movie series and a bit of a silly one but it did allow for a McGuffin that added depth to the Dumbledore/Grindelwald dynamic.

Frustratingly, it would have been FAR better if it had turned out that Dumbledore had intended for Newt to use a Niffler to take the oath vial all along. That would have fit in with this being a Fantastic Beasts film, fundamentally, and it would have fit in with Newt working out that Dumbledore sent him to America in the first place for a secret reason. Without that, the idea that Niffler just ACCIDENTALLY stole the vial is a bit stupid.

Anyway, how ever we got there, the vial is now in Dumbledore's possession and one of the barriers to him fighting Grindelwald is gone. Yes, he will still have to wrestle with being in love with him (since he was still his greatest desire according to the Mirror Of Erised), but the thing that was being held up as him not being "able" to fight him throughout the movie is dealt with.

Presumably, the next film will explore their relationship a little more as well as Dumbledore's residual feelings and his attempt to find a way to break the blood oath. But the key thing here is that all Dumbledore has to overcome is his emotional attachment (with the clever caveat that Rowling wrote in a stronger reason for him not having done that already, avoiding making Dumbledore coming across as a fool), so he has a means to get to his enemy.