https://youtu.be/eOlbdCE-EoI?t=134
In this scene it is stated that the memories of the keyblade wielders from the keyblade war were overwritten with new experiences. Possibly it could have been overwritten by Brain or maybe someone else? Maybe Strelitzia?
https://youtu.be/nyC3XXcDTS4?t=66
In this video you can see Strelitzia is panning back in and out of existence. This might be because she created a heartless and nobody after she was attacked and released her heart:
Suddenly, someone comes out from the shadows and attacks both Strelitzia and her Chirithy, stealing Strelitzia's rulebook. In her last moments, Strelitzia laments how she did not have the courage to speak with Player, carrying her Chirithy in her arms as she fades and her heart is released.
She might've created a nobody under the same circumstances that namine was created.
In Ansem Report 9 it was stated this was how namine was created:
Naminé is a Nobody, created when a young girl's heart left her body.Yet she has no corresponding Heartless.This is because the "young girl" in this case was a princess.Kairi, a resident of Radiant Garden over which I had ruled, was one of the Seven Princesses that uphold the realm of light.With no darkness in her heart, Kairi produced no Heartless, and instead of vanishing, her body remained in the realm of light.In other words, both the Nobody called Naminé and the Heartless—proof of a lost heart—are extremely unstable beings who lack the bodies needed to produce a Nobody
The panning in and out of existence that you see in the video of Strelitzia might be the result of her heartless being an unstable being as stated in this Ansem Report. Her nobody that was created from this might be the one to be able to rewrite the memories of the keyblade wielders that fell from the keyblade war. And maybe Brain was the one that struck her down in order to create a nobody from Strelitzia in order to alter the memories of those keyblade wielders in order to change the events in the book of prophecies.
It might also be possible that Strelitzia has a pure heart because she might be a princess? Im pretty sure I'm going far out for this one but Larium and Strelitzia might be Prince and Princess. And that Strelitzia has a pure heart, but I have zero evidence for that and I could most likely be wrong. But this would help the idea that Strelitzia was able to create an unstable Heartless (which is the panning in and out of her in the video above) and a nobody (like namine) that would be able to alter the memories of people.
But in order to change the memories of all the keyblade wielders they would have to be connected with someone just like with Namine Secret Ansem Report 9
That is, Naminé is an alter ego of the Kairi who has directly interfered with Sora's heart. Could this be why Sora and those hearts are connected to him were able to have their memories controlled?
Strelitzia mightve been able to alter the memories of Ephemer and all of those who were connected with him as seen in the fight in KH3 at the Keyblade Graveyard. How this is possible I have no clue. It might not even be true that Lauriam and Strelitzia are Prince and Princess. Lauriam does look like he can be a prince and Strelitzia does look like she can be a being of a Pure Heart. In this picture you can see who corresponds with who in the story of KHUx:
https://www.khtheories.com/wp-content/uploads/2017/09/KHUX-2nd-anniversary-art.jpg
So Lauriam and Strelitzia are across from each other. Brain and Skuld are across from each other. Ventus and his Chirithy are across from each other. and Ephemer is the main character in the story.
I don't know if it is true that Lauriam and Strelitzia are prince and princess or that Strelitzia has a pure heart but who knows. This could also be why Marluxia is the head of Castle Oblivion, the place where they used namine to change and mess with soras memories. This theory is very farfetched but some things sound kind of right to an extent.
Also in this video you can see Lauriam is very worried about Strelitzia just like the princes in the disney worlds worry about the princesses in the game (ie: the prince goes after cinderella, sleeping beauty and the prince, and so on).
https://youtu.be/nyC3XXcDTS4?t=92
This also happens after Elrena/Larxene tells Larium/Marluxia about Strelitzia.
This could also pertain to this scene in KH3 as well
https://youtu.be/gPV2opGNFyo?t=27547
Larxene/Elrena could be referring to Laurium/Marluxia in this scene. Also in this scene she says "My secret"
You can refer that part to this scene in KH3 when Sora talks to the nameless star. The nameless star refers to the person that she is talking about as Our Secret
https://www.youtube.com/watch?v=S2Deu9mNbHc
Heres a link fast forwarded to the part where she says Our secret
https://youtu.be/S2Deu9mNbHc?t=190
This nameless star could be Strelitzia who is referring to Larium/Marluxia as the person shes talking about, it also might be why Namine is in this world as well but who knows though
Spoiler Show
