Outline:
Herobrine remained behind to battle The Wither.
The Warden(s) remained behind to support Herobrine and discourage the discovery of Strongholds.
Illagers and Pillagers are indigenous natives who learned from the hubris of the Builders and their former worship and admiration of them.
Originally Imitators, Villagers continue mimicking The Builders while Illagers constructed mansions filled with imitation crafting and reminders of what The Builders had done to them in the way of mock End Portals.
Pillagers are the resulting Illagers after The Builders vanished, seeking out and destroying any and all remnants of Builder lifestyles and activities.
Before The Beginning, The Builders simply created massive structures and labyrinths, crafted all manner of materials, goods, tools and weapons, and maps; simply seeding the basis for Civilization and setting the example for the indigenous inhabitants all across the infinite spectrum of individual worlds, until they came upon a singular world with infinite potential…
In a sense, even, they became trapped in Minecraft.
But they would not realize this until they tried to escape their own hubris.
At first, they discovered world “seeds”, enabling them to visit the same world an infinite number of ways. So they explored thousands of worlds for the first hundred years or so. Eventually, not knowing these worlds were all intrinsically connected and affected by one another, they started building small villages for themselves and the natives.
Soon, however, they would find that other seeds they’d visit would, surprisingly, exhibit similar and even identical structures and communities already inhabited by villagers.
It was as if everything they did would instantaneously copy itself across the entire spectrum of Minecraft…
… BEFORE The Beginning, this was not seen as a problem or a matter for concern as they spread across the world’s seeds, seeding civilization in their wake until they developed an urban biome of science, technology, and magic.
Meanwhile, all the time, the indigenous natives had become great imitators and evolved, more or less, into Villagers. The original Villagers were Imitators of The Builders, and attempted to craft everything they saw the builders craft, with marginally less success.
It was not until The Builders revealed their portal technology which enabled them to enter this world did they discover that they could not return from where they came… And they discovered the existence of The Nether.
Their technology created an as-yet-unknown one-way entrance to Minecraft, but did nothing to allow escape.
A large, black, metallic “doorway”, as far as the Imitators witnessed, which The Builders attempt to activate with some kind of electrical spark, only to no effect. They reconstruct and attempt to activate it multiple times, each with no greater success than the last.
In an extremely unlikely but hilarious case of irony, the Imitators created another bad imitation out of obsidian. Except this time when the Imitators applied their spark, or rather lit it by flint and tinder, it “worked”.
The Builders watched in amazement which quickly turned to distress as the villagers entered the portal and succumbed to The Nether...
… The Builders attempt to protect the Imitators and Villagers, as well as themselves, from this unknown realm by erecting terrible Bastions and Fortresses in The Nether: The hostile inner-world below the bedrock; which turned out to reveal terrible secrets and ghastly consequences.
As The Builders fought the endless onslaught of Magma Cubes, Ghasts, Blazes, and other monsters, many, MANY Builders had died before they could be healed and before they discovered how to craft Totems of Undying; and were buried in the Netherrack.
This would inevitably lead to the creation of zombies and Wither Skeletons, as the Netherrack’s otherworldly properties included flammability without extinguishment and the transmutation of souls…
The tragedy was such that the body would “melt” into the Netherrack and the breath, or soul, would become trapped in the body by the heat of the Netherrack causing the lower “soil” to become a sandy substance charged with the soul of the departed. The leftover bones were unnaturally dark and black, covered with the charred flesh remains.
The Builders were an exceedingly industrious and scientific race whom would inevitably experiment with the soon-discovered soul sand.
Their discovery of soul sand would mark The Beginning of their End.
By now, the Imitators have learned a lot about science, industry, and magic; Explorer Builders inspired Imitators to become librarians and cartographers. Miner Builders inspired Imitators to become stone cutters, tool smiths, and armorers. Farmer and Hunter Builders inspired Imitators to become farmers, fletchers, shepherds, butchers, fishermen, weapon smiths, and leather workers. Architect Builders inspired Imitators to become masons… and Mage Builders inspired Imitators to become Clerics. They revered The Builders as Gods, but their “gods” have not yet learned everything about this world, or The Nether... Much less how to get back home.
They begin seeking means of resurrecting their dead... Inspiring Imitators to become Witches and Evokers…
Everything they knew about physics, from where they came from, was only 85% accurate here. Or, more accurately, only MOST of what they knew “worked”. The Builders' resurrection magic and hydraulics and wavelength technology were utterly and completely useless to them here.
In their efforts to bring their fallen back to life, their failure inadvertently leads, again, to the Evokers’ “success” ... and to The Builders' utmost ghastly horror, their own become permanently lost forever to Minecraft, roaming the infinite seeds as Skeletons, Husks, Drowned, and Zombies.
By this time, it's too late to save anyone who has already passed as the event is repeated simultaneously across all the infinite seeds.
Now, this time, The Builders unknowingly discover their fatal mistake of imitating the Imitators.
They saw how the imitators would arrange the fallen bodies in a “T” fashion before affixing the skull, and experimented, but when they arranged the soul soil and affixed the head of the fallen, nothing happened.
The Imitators discovered they could create Iron Golems and Snowmen by imitating the imitation of their “success” (of undead monsters).
The Evokers discovered they could reanimate the charred bones and created Wither Skeletons.
The fear of losing their fallen to Evoker magic, and the quirk of a carved pumpkin, encouraged The Builders to try things a little more… creatively.
And when they adorned the soul soil with THREE skulls of their former comrades-now-Wither skeletons, they unleashed THE Wither: a three skulled, legless, flying, BOMBASTIC skeleton, spewing forth projectile explosives everywhere.
They now begin recruiting Imitators, teaching them how to mine and build, but not craft, until they could construct Strongholds deep underground near the bedrock.
This project would take them decades, over which time The Wither would effectively decimate everything on the surface.
No more skyscrapers, no more infrastructure, no more science, magic, technology, or feats of engineering remain. Within 5 years, The Overworld Surface is returned to Minecraft's wilderness as The Wither erases all but the simplest or the most hidden structures.
Not just deconstructing things, but REMOVING them from the seeds.
The first year was devastating to The Builders as they learned the consequences of The Wither's power. They could not escape it by visiting other seeds, as it seemed to be intrinsically drawn toward their very existence, but quickly discovered the extent of it's ability to revert Minecraft toward its native state.
By the third year, they had all but completely abandoned the surface and the few who were not hiding in Strongholds were rescuing Imitators from the surface.
It was later due to the daring bravery of one particular Builder, already famous for rescuing many Imitators during these times, that led to further mixed events and the resulting Wardens.
By the tenth year of The Wither's reign, The Builders had devised a strategy to cooperate with the imitators and teach them proper crafting abilities and to, hopefully, (re)construct a new portal home.
However it is around this time that that one particular Builder, Brien, took it upon himself to enchant his armor and wage battle against The Wither.
The Hero embarked to the surface leaving behind the promise of salvation, but by the time he had returned, there was nothing left of The Builders or the original Imitators. He would inevitably spend twenty years locked in a battle with The Wither, and survival; learning how to hide, craft and build in secret, and move with the utmost stealth. He crafted a sonar device called a Shrieker to help him keep tabs on The Wither's whereabouts without revealing his own location, and though his activity against The Wither was seldom witnessed by survivors, every so rarely would an Imitator follow Brien and attempt to imitate his stealthiness and fortitude. His efforts to hide the existence of the Strongholds and his persistence against The Wither inspired Imitators to become Wardens, eternally diligent in warding off all explorers from the depths of Minecraft.
By the time he returned to his Stronghold to find a sign with his name misspelled, "Where is the Hero, Brine?" he was so exhausted, confused, and alone, that he wore the name like a badge.
Hero Brine continued to roam the worlds of Minecraft in secret, occasionally leaving traces of evidence that he exists, making sure The Wither stayed dead... for a time... He has since appeared to have.... vanished... Maybe he found out how to activate The End Portal...?
Meanwhile before his return, deep underground in their strongholds, experiment after experiment was attempted with the audience of eager Imitators who would then attempt to recreate whatever they witnessed, of the creation of a technological portal between dimensional gaps of time and space.
Eighteen years of education, exemplification, and imitation until they finally created The End Portal.
The Builders secretly crafted the keys to activate the portal in hopes to hide Minecraft and protect others from finding it; a secret that would inevitably be lost along with The Builders themselves. Combining these Ender Pearls with Blaze Powder, they create the actual key to activating the portal and begin sending Imitators through with instructions to return promptly...
But nobody ever returns. For two whole years both Builder and Imitator alike go through the End Portal (So named because nobody ever returns) until, finally, only the last builders and a few imitators remain.
The imitators, indigenous to Minecraft, without nearly as much concern for the Wither above and silently aware of their intricate and intrinsic connection with the Minecraft Seeds, began refusing to go through the portal shortly before the end of the second year, and had now developed mixed feelings for their guests. Some hate and scorn for The Builders settled into various Illagers such as Vindicators and Pillagers, while the imitators that remained, all of whom were not taught by the builders (those who crafted the portal were eager to test their creations, after all), could think only to return to the surface and continue surviving as they've learned how, thus becoming Villagers.
Minecraft's Overworld as well as it's Nether have not since seen The Builders, but in no large measure of time, Endermen began to appear in the Overworld.
Those in the Overworld today are almost completely unaware of the prior existence or influence of The Builders and none know either what happened to them or where they came from, IF they even know about them at all.
But if you ask me, Master Architect Redundant Jovian Thor, I'd tell you that they were clapped back by their own hubris even after the last of them entered The End Portal.
The last ones through were greeted with a great deal of shock and terror as they entered a VOID populated by DRAGONS!
Yeah, I'm kind of exaggerating things a bit, you know, to set the mood? I dunno, but hey, bear with me...
They kinda took their time, being the last ones through the portal, over the 2 years or so.
The first builders through definitely did not last long, but I couldn't tell you much, since I wasn't there.
But I never was either. (you're probably going to wonder how in the heck I can know anything about this, but all I can say for now is that it comes with the territory)
All I know is what those last two builders know:
The first (surviving) builders established some kind of bunker and began constructing flying ships to wage war against the dragons. After the twentieth or so wave of new Builders to The End, they had constructed at least two ships and could set out into the new realm and hold a fighting chance.
They kept guard of the bunker for a long time before damage finally led to its abandonment, but not completely. It was the last week of waves, when The Builders in the Overworld were getting more anxious and sent waves more frequently, that saw the most devastation and destruction.
End Dragons had powerful magic that had turned most of the builders into Endermen who constructed great obsidian spires topped with Ender Crystals to heal the End Dragons.
The Battle was swiftly being lost on both sides.
Dragons, being ancient creatures of exceedingly long lifespans, did not breed frequently enough to repopulate to replace their fallen numbers, and the Builders were mostly Endermen by the time my two friends finally found their way through that accursed portal.
The End Void was an adventure of their lifetimes, but a very valuable journey, indeed.
By the time Alex and Steve entered The End Void, there were only a scant few hundred Builders left to escort them to the End Cities they constructed, but End Dragon magic or not, they were left to eat Chorus Fruit, which slowly transformed them into Endermen anyways.
It appeared that all was completely in vain, that there was nothing left but to accept The End.
Steve and Alex refused to eat the Chorus Fruit and retreated into seclusion and deep meditation, far away from the dying Builders and arising Endermen.
In the Void between The End and the End Cities, While The Builders brought the End Dragon population down to one, Steve and Alex found the way out and left a story behind for anyone who made the same mistakes as The Builders: by killing Jean, the Last End Dragon.
And for anyone concerned with her safety, Steve and Alex also left behind a few extra crafting recipes to revive Jean, just in case.
