Here's the summary of the story and what I have so far below that.

It's been barely two and a half months since Jason's attack. Nopony really knows how to keep their life going except to either improve, ignore, or lash out.

These reactions are placed to the test when an armed human gets transported there from another Earth, this one under attack by another Equestria who's threatening the complete extinction of the human race.

Complicating things is how will this new human react in response, especially when the Griffons and Dragons offer to make him their king/emperor, and when yet another human world offers their Allegiance?

. . . . . .

Confusion.

Confusion, terror, and overwhelming sorrow.

That was the majority's reaction to the confused and nervous male human who showed up in front of them. This was quickly hidden by semi-happy smiles and welcoming postures.

"H-h-ello! My name is Twilight Sparkle, and I would be glad to be the first to welcome you to Ponyville and Equestria!"

"T-thank you. Um- is it safe to say that I took a wrong turn in that-? Oh, who am I kidding? I knew I shouldn't have clicked on that link…"

Looking around with clear relief while lowering his strange stick, he came to a conclusion that left Twilight and her friends gobsmacked.

"At least this Equestria isn't threatening my species with extinction…"

You could have twilight Turns into almost a caretaker helping him out any way she can but also hiding anything to do with the previous human and what they did possibly even hiding him from the princesses you could reason it as She's trying to make amends in a way but she knows if the princess finds out she may never see him again and if Jason finds out it might end bad there's the other route I can think of Is that she tells the new han of what happened and he comes to mistrust them Possibly going on a journey to find Jason or find a way back by himself maybe in the ever free maybe buffalo lands idk just spit balling ideas there's also the question how dark or "light hearted" for this universe are you going to make it and how spiteful are each over the six and ponies in general of humanity at this point also how well armed

As for the other part with allegiances of that many creatures I assume the human would try to find a way home to push the ponies back and with take kinda of man power it would be a rout unless to other humans were more primitive or they have some amazing artifacts if you do use this for the story a good plot point might be how the relationship between ponies and non ponies reach a critical level worse than before dragon griffons and humans have to live beside ponies in one world that has been known to mistrust and treat other races and one that is out for blood lete know what you think of my ideas

7830792
I'm definitely loving it. I'm aiming for it to be semi-dark, with spots of hope and humor, while also having splotches of blood, if you understand what I mean.
Also, the human is from a world that parallels our own, but TCB!Equestria is more militarized and violent because of Sombra and Tirek's rampages, thus giving his Earth more of a fight.

7831305
Nice can't wait for this story I have a feeling it's going to be fire pm or reply to this if you need anymore help