The War of the Battlefield

It has been years since Melee. The War of the Battlefield is over. The World of Smash is recovering. That is what it may look like on the outside, and it also may be what many want it to be. A world of peace is far gone for this world, as trouble is brewing beneath the surface.
The Mushroom Kingdom has been seized by Lord Bowser, King of the Koopas, and he has forced the princess, Peach, to be his queen. Mario is merely a lowly servant, forced under the slavery of the monster, the narrative completely changed.
Hyrule's Princess and Hero have been enjoying this newfound peace, however the omen of darkness comes when Zelda begins having strange visions... and a voice in her head is warning her of dark times to come. And on top of all this chaos, a new hero has arrived at her doorstep, a brand new Link, further adding onto this cryptic omen.
In the lands of Fire Emblem, a mysterious man claiming to be the long dead Hero-King arrives to challenge King Ike to a duel as well.
None of this can be a coincidence... or can it?
What does this all entail in the World of Smash? Buckle in for an epic story of war, blood, and tears. And also...
DEEEEEP lore.