Aura and Methius have been creating Necrobies for years. It started small, and they never insisted the Bies had to come with them, or stay in a group. The magic of Necrobies suffused into the world, and inspired by emotions of the humans, fae, and really any sentient creature, the toys and plushes burst to life. Each had their own life, their own point, their own priorities, and the Stitchwitches encouraged them to grow and explore them with their new liveliness.
However, Bies often found themselves drawn to one another, and so the Stitchwitches looked to their beloved Bies, and began working to find safe spaces for them. The first was a small forest in which they could build a neighborhood - lovingly named Shop Street by the local Bies. They worked to build portals to the different settlements of the Bies, trying to keep all safe; this already let Bies reach one another and visit different folks. As the numbers of Bies grew, though, they knew more was needed - a safe place for all Bies to be able to be together, if they wanted to be, or to return to whenever they needed.
Putting their powers together, along with the powers of new magical makers, the Stitchwitches and Knitwit came together to create a safe civilization. Aura's love, Methius' patience, Courduroi's joy, and Charger's calm - and all their talent and creativity - poured into a hidden group of islands, lost in the Bermuda Triangle where most dangerous humans don't dare to go. Moving their settlements - and the Bies who call them home - safely into the Triangle.
Thus, the Archiplushago was settled.
While Bies can still leave the Archiplushago, this is a safe haven for Bies and all their creations. There are multiple settlements there with different types of Bies, and even a big Church out in Lacelorn (though a questionable Angelic bie has been sighted). The original "Shop Street" was moved as well, becoming PLUSHOPOLIS, the center of the Archiplushago. and the main city for Necrobie society. The Plush Palace is in the center of Plushopolis, in which the Stitchwitches and Knitwit all have their own homes for when they visit the Bies.
The Plush Palace is very engaged and open, and Bies come and go all the time. When you visit the Palace, you are able to go inside and explore - Azuca's room is in the Palace, and he's often found working there to care for Bies in different ways. Just don't wander far alone - there is a labyrinth in the center of the castle, easy to become wanderlost in. This protects the Lifeline Lake, the center of the magic used to create the Archiplushago. It's said there is a beautiful crystal, created by the combined magicks of the four Creators, that keeps the Archiplushago safe and sound from any negative effects of the Bermuda Triangle, and hidden from human eyes.