Illager idea (if we are counting the whole family of mobs as illagers)
Aeons ago, during one of the many heights of illager control, they did what most civilians do
They started research into things that wernt to be meddled with, things like the source of a totems power, the light of a nether star, the potions that they had relied on so heavily to get where they are now
They found things that were fascinating, things that were powerful, leveling cities on accident, making the night as bright as day, creation of the ravager (turns out regeneration is quite volatile)
One of the last things they did before that era ended was figure out said ender pearl, and the corrupting force that came with it
With a grant from the prison, they took a pillager who had tried to run from the wars, horrified at what he saw, and they subject him to the pearls corruption
When they finally checked in on this unnamed pillager though, there was nothing in the chamber, not even the cracked pearl
when they opened the door to see what had happened, as a sealed room without even really ventilation shouldn't be possible to escape from, they heard the noise of a crossbow being drawn back
And the illusioner revealed himself, and with it, his 3 copies
Not even the guards stood a chance against him
Upon his escape, he considered his options, maybe he could overthrow the entire civilation, bring end to that which he hated, or he could flee, find a new life, let the illager kingdom die on its own
Fleeing through the nether, he collected many things, most importantly, gold, netherrack, and a fire charge, which he used to make a campsite in the overworld
9 gold blocks, 4 redstone torches he stole in his fight, 1 netherrack, and fire atop, he brought about the devil, destroyer they called it, and with it came the creator
A pact with the devil and a fleeting glance at the creator, he hid from the world, never to be seen again
We now know the destroyer and the creator as Herobrine and steve
(did I go too hard on the story part and not the head cannon part? Please let me know)
Oooh, fun story! Got me hooked ^_^