Matters of world destruction

Apocalypse is an exceedingly simple matter when you are a victim of it. To resist or to surrender, you are faced with the same sight of world-ending powers crushing everything with the unstoppable force of a natural calamity. Why should it matter to you what happens when all have died and when all that has been built up is erased? It's all the same in the end. You and everyone and everything are gone.

But the matters of world destruction is not what it seems. Killing every organism, even disintegrating every object down to its last atom - that is not the objective of destroying worlds. In the first place, for a foreign entity to enter a world was supposed to be impossible until the Legends of Youth attacked.

The Otherworld Rules

Think of a world as as a singular, unique biome. Organisms in that biome flourish because they are suited in the conditions of their environment. If put in a different biome, any slight change can lead to the extinction of a species. This is infinitely truer when it comes to physical bodies, replacing "biome" with "story." Attempting to enter a story when you are not suited to it would be excrutiatingly painful as doing so would cut you off from your connection to your native story. If, somehow, you managed to slip in the world, your unsupported existence will be terminated in due time.

Even a Fabled soul would not stand a chance. Yet, it is one of the requirements for the Legends of Youth to trespass into a world and do what they will to its story.

Sulfiric Soul

One's existence is tied to one's soul. By reaching into the blueprints of one's existence, they can evolve into cosmic dimensions. For beings in the material realm, this isn't possible without divine miracles like true reincarnation and messianiac agencies.

After the ascension of legendary Pokemon to godhood - becoming uncontested laws through all realities - they have scattered about their influence through the power of RUNES. As it is a recent phonemonon, not much is known about Runes except that it emerges from souls whose existence have become a blazing star. Naturally, there aren't many souls like this. Until recently, in fact, there were no such thing. But when the Legends of Youth summoned Fables from the canon legends, these Fables would appear bearing a GATE CREST. This phenomenon would repeat with Dreamers who had their worlds destroyed and again with latter Fables summoned through the same method as their predecessors, the Destroyers.

The Gate Crest allows a direct connection to the soul. With this handy tool, ascension has become a distinct possibility. When the bearer has accumulated enough experience - enough "stories" - the crest will mature and like a fertile patch of land, a Rune will grow from there.

The Rune is a separate subject but as far as destroying worlds is concerned, the important part is now the soul can stand being in a foreign world. By forming a bond with such sulfuric souls (called sulfuric as stars and space in general do not smell pleasant), the Legends of Youth would break through the Otherworld Rules with no problem.

All that work and it's not even part of world destruction yet.

Killing Stories

The matter of world destruction, as mentioned at the start, is not about the physical phenomenon. Even if not a speck of space dust is left, the story of that world still exists. It's like a code in a program that's still around even if it can't be observed or manifested. Stories that are not from the Canon Legends have lifespans, so the only way for the "code" in this context to disappear is to let it disappear by itself.

But as we know, the goal of the Legends of Youth is to preemptively destroy them - to hasten the process. Truthfully, this is impossible to do. No matter how powerful or violent they are, they will not be able to do anything about the story's lifespan. But the clue on how to kill it is right there. The only thing that can do something about the story is the story itself. To destroy worlds, the Legends of Youth would have the story kill itself.

"Flowerbeds"

With the Destroyer and their companion, they bring ruin to the invaded world. Majority of thel locals (if not all) would have perished by then and would no longer be concerned of what happens next. After this stage though is the most important part. With most of the landscape gone, the world is then left alone and sent "flowerbeds." It is more accurate to call it a pit or the abyss, but it received such a name due to the strong aroma of blossoms from the bottom. And from this hole, corrupted Pokemon fueled by the despair around their environment are unleashed. Due to the shadowy aura covering them, they have come to be known as "Shadow Pokemon." But with their very nature changed from companions to unearthly nightmares, those who have lived long enough to witness them refer to them as monsters. Terrors.

While Shadow Pokemon are beings who desire to bring suffering onto others, the purpose of breeding them in these ruined worlds is because they count as foreign entities. With their numbers and their souls being empowered by hate, they are gradually overwhelming the story of the world, distorting it into something that can no longer support itself. Like a virus sent to attack it from within, the story will eventually break in its attempts to repeatedly fix itself, thus completing the destruction of the world.

After the End of the World

With the story gone, there is nothing left but the foreign entities left behind in the world. The flowerbeds have another important task. Like a parasite, they take control of the void where the story used to be. By absorbing the Shadow Pokemon, it creates a eternal labyrinth where the lost souls of abandoned Pokemon wonder. As it is a pocket dimension, it blocks off resonation from other worlds, additionally serving as a buffer that will not disappear until the master of its story is defeated.

Unknowingly, many have already visited such places, both in Paradox Paldea and in the Pokemon world. These things that are known to them as mystery dungeons.