>>93135961What you need to know:
Xehanort had made multiple clones of himself, some of which are his past selves, because the 3DS game had time travel. The others are Nobodies from Org XIII he had 'taken over'. Xehanort wanted "13 Darknesses", the new Org XIII, to clash with the "7 Lights" to create a powerful weapon from Kingdom Heart's past, called the Chi-blade.
The PSP spin-off, set before KH1, introduces three keyblade wielders, who all end up in various states of distress: one is "taken over" by Xehanort, one is stuck in the world of Darkness that you see at the end of KH1, and one is 'sleeping' because of some complicated Darkness experiment. Just go along with it.
Sora and Riku, in the 3DS spinoff, are in an exam set up by Yen Sid to give them the powers to awake the "sleeping" people. They do this by going into "Dream Worlds". Riku passed the exam, but Xehanort sabotaged Sora's, and in the end Sora is taken over by Darkness, becoming the final, 13th Darkness that Xehanort wanted.
Riku (and others) saved Sora, but as a result of the sabotage Sora is returned to being a weak piece of shit. Sora, Donald and Goofy went to Olympus Coloseum to restore his powers, and this is how KH3 will start, apparently. Riku and Mickey went on a mysterious quest together. Kairi stayed with Yen Sid to train her Keyblade powers.
The DS spin-off detailed how Roxas can dual-wield (there's another Keyblade wielder inside him), the other DS spin-off detailed the creation of "Datascape", a world Mickey creates from Jiminy's journals that Maleficent wanted, and the mobile phone game is set far in the past, where apparently everyone is a Keyblade wielder. Not sure about the mobile game's connection to KH3.
There are so many things I skipped, but I think this should be enough to start KH3.
