Who are the mysterious legion? (Contains Major Spoilers)

Warning, this post contains some major spoilers.

So, if you don't want to know, don't read it.

During the battle with the heartless in the Keyblade Graveyard, Sora encounters Lingering Will (at least I think that's him). So, after he says 'so, want some help?', 1000's of golden keyblades come flying in and attack the heartless tornado. During this time it says to keep attacking with the mysterious legion and there are tons of names, which appear to be player names as you spam the triangle key. Who are these names? Are they random PSN player names that are playing the game?

Supporting Image 1:

Supporting Image 2:

Those names seem to be taken from

player names in the mobile game Kingdom Hearts Union X [Cross].

This is further supported by a quote from

Ventus (or was it Roxas?) who says the Keyblades were "lights from the past". The mobile game takes place before the first Keyblade war.

And the final similarities are

the logos next to the names in Kingdom Hearts 3 are the faction logos you can choose from in the mobile game, each representing one of the five Foretellers

The spoiler wouldn't work without this line so the image is below

From a player who has played all the games I have your answers.

The person who shows up to Sora asking if he needs help is a character called Ephemer. He's from KHUX. The mysterious legion are the players from KHUX that got picked from lottery event to have their name in the game.