"Spoilers
During the game Kirby is pulled into an Urban World that has been abandoned and taken over by nature. Kirby in his journey to save the Waddle Dees that have been pulled in with him discover that an Alien named Fecto Elfilis attacked the Planet only to be captured by the Planet’s inhabitants and exploited for their Planetary Warp Technology which they exploited to ditch the Planet for a Land of Dreams after Elfilis split into Forgo(still captured) and Elfin(the Good Half which had escaped).
The implication seems to be that the Forgotten Land that Kirby, Meta Knight, King Dedede & the Waddle Dees were pulled into was King Dedede & the Waddle Dees’ homeworld!
Of course since the universe of Dreamland includes threats that the Ancients and other beings defeated. Something that Hyness called a Nightmare of a crisis during Kirby Star Allies!
Seems like Fecto Forgo went and decided to take his revenge out on the Waddle Dees by unleashing Nightmare upon their Dream Universe(they live on almost every Planet of said Dream Universe) only for the Dream Natives of Magic known as the Ancients to fight them back along with the Faction aligned with Science(presumably the Waddle Dees) only for the Magic Users to be banished because the Science Users were scared of the Magic Users.
Maybe a DLC will confirm this! Anyone else hopes so?