In Fantastic Beasts: The Crimes of Grindelwald we found out that Grindelwald and Dumbledore

made a blood pact so they cannot fight each other. The memory Albus saw in the mirror implies that they did it out of friendship.

But it seems to me, that there is no time when this could have been made. In the time of the movie Ariana Dumbledore is already dead (Albus said that to Leta in the Hogwarts).

We know that Ariana died in a fight between Grindelwald, Dumbledore and Aberforth as described by Aberforth, i.e. on Pottermore site about Ariana:

I pulled out my wand, and he pulled out his, and I had the Cruciatus Curse used on me by my brother’s best friend – and Albus was trying to stop him, and then all three of us were duelling

So at that time

the blood pact couldn't be already effective. They obviously could fight each other.

But on the other hand, it would be strange if

they would make this pact after Ariana's dead, they weren't friends anymore after this event.

So, the question is obvious:

When was the pact between Grindelwald and Dumbledore made?

closed as primarily opinion-based by Bellatrix, TheLethalCarrot, Skooba, Mat Cauthon, Jenayah Dec 7 '18 at 15:03

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

  • The pact must have been made before the duel but it couldn't have been long beforehand. – TheLethalCarrot Dec 7 '18 at 11:44
  • @TheLethalCarrot If it would be before the duel, they wouldn't be able to duel each other. – TGar Dec 7 '18 at 12:58
  • There’s no explicit details on what actually happened during the duel. For all we know they didn’t actually duel each other. Or some spells were “allowed”. Or the act of casting a spell against one another made it rebound and hit Ariana. At the moment all we have is speculation. – TheLethalCarrot Dec 7 '18 at 13:02
  • @TheLethalCarrot We now they were dualling, it is even part of the question as a citation from Pottermore: "all three of us were duelling". Maybe something was allowed, but it wouldn't make sense to have such pact with allowing spells that can kill a person. – TGar Dec 7 '18 at 14:16
  • 2
    I'm voting to close this as per the Future Works Policy as this will certainly be addressed in the upcoming films. – TheLethalCarrot Dec 7 '18 at 15:00