(This article shines for love, but please don't read it if you are interested in the party, because the details are different, and the author is very lazy. He is too lazy to make changes and has to fill in the holes on the spot. But there is an outline, so try to fill it in as soon as you have time.)
After Grindelwald was struck by the death curse, he was reborn as a young man, back when he was still studying at Durmstrang and had not been expelled.
Since Merlin's magic allowed him to go back to the past, he might as well fix all the regrets this time.
His regrets are actually not many, including the wizarding world, the Muggle world, immortality and Dumbledore.
Conception:
