Millenim is a planet from Kirby: Nature's Hero.
Millenim is not very advanced, roughly equating to 13th century England in regards to technological development. A form of machinery called Timbertech, which involves magically enchanting wooden contraptions, is frequently used here as a substitute.
The planet has customs which take place over a thousand years, true to its name. In particular, every thousand years, the citizens of the planet steal natural resources from another planet in hopes of using them to help the planet thrive. Species who live in Millenim are also depicted as very long-lived, being able to live to almost a thousand years old.
Millenim's population mostly consists of tame, independent races such as Waddle Dees, although it also has two notable groups residing there, those being the Skeleton Kingdom and the Rose Empire.
The Skeleton Kingdom is ruled by Emacian, a corrupt being who uses the guise of being King to commit crimes all across Millenim and all manner of other planets, all the while possessing his adoptive son, Arcadava, in order to cover up his tracks. In actuality, however, Emacian intends to use these villainous actions in order to disguise his ultimate plan to gather enough energy from the Tyrian Lava, a substance found only in Millenim, as so to become the godlike Skeleton Eye and destroy all foreign planets as so to take their resources and use them to make life on Millenim eternal. After Kirby stopped this plan, Arcadava returned to his senses and took charge of ruling the Skeleton Kingdom peacefully.
The Rose Empire, on the other hand, is a more uncivilised nation ruled by two sisters, Scarlet and Canary. Scarlet is somewhat sadistic and likes embodying fear, whereas Canary is soft-spoken and believes there is a peaceful solution to anything. The two sisters, despite ruling together, dislike one another to the point that they both refer to the other as "the girl next door". Shortly before the events of the game, Scarlet locked Canary inside Access Orb, a huge prison made solely out of Timbertech. When Kirby destroyed the Access Orb, however, the sisters suddenly had a change of heart, made up and returned to looking after the empire in peace.