Discussion 400 Years Ago

[Hermit]

So, in the light of the most recent chapters where we're dealing with all the events from 400 years ago as from Natsu's perspective, I decided to make this thread to discuss and speculate on what other matters you think happened 400 years ago.
What we do know so far about 400 years ago
-The Dragon King Festival, where Acnologia killed over 10,000 Dragons, which are all sleeping in the graveyard under Mercurius right now.
-Zeref's family was killed by a Dragon that attacked their village, and he lost everyone, including his younger brother Natsu.
-Zeref was cursed by the God Anksherum for playing with life and death, and successfully reviving his younger brother as his strongest demon, Etherious Natsu Dragneel.
-Zeref created several demons, with which he hoped could end his life, and the demons all banded together to form a guild called Tartaros, under the leadership of Marde Guille.
-The souls of the Parent Dragons, Igneel, Metallicana, Grandeenay, Weisslogia and Skiadrum were extracted by Acnologia's Dragon Slaying Magic.
-The Eclipse Plan was devised, and Natsu, along with Four other Dragon Slayers,Sting, Rogue, Gajeel and Wendy, were sent 400 years to the future, where Ethernano was at a high enough concentration to allow the Dragons inside them to recover.

Spoiler: Anna

-Anna made Natsu a scarf, which as we were shown in Tenrou Island, is a direct counter to Zeref's Curse.

These are all canon facts, all confirmed in the manga.
Now, for the second part of this post, which deals in speculation more than anything.
What MIGHT have happened 400 years ago
-The Book of E.N.D was stolen by Mard Geer.When the CSK was summoned in Tartaros to fight the King of Hades, his first words were how Mard still held on to the Book.. This means Mard wasn't the one entrusted with the Book initially. There was someone else that Zeref had given the Book, who Mard stole it from which resulted in a fight between him and the CSK, that Mard Geer won.
Who was the person in question?
Anna Heartfilia, the strongest Celestial Wizard.
-Anna's death, which came as a result of Mard Geer attacking her while she had the Book of E.N.D in her possession
-E.N.D, Zeref's strongest demon was sealed away. This was due to him encountering Igneel who failed to kill him because he loved him.
What other events do you think happened 400 years ago? Or do you think we'll see more of 400 years ago?
If you have a thought, you are free to elaborate it in this thread.

 

[GamerSkull]

The Nirvits also went extinct because of Nirvana 400 years ago but I'm not sure if that'll come up again regarding the Dragonslayer plot, same with Eclair's receival of immortality in the movie which was also 400 years ago.

I'm guessing Anna was the last one to summon the CSK against Mard Geer since they both seemed to know each other. If so, I wonder what key she sacrificed. Perhaps this is also why the CSK calls Lucy "old friend."