Basically
Pre black souls 1
Jabberwock in her curiossity and immensse boredom decidesss to make the blackest soul, or rather wishes to see the blackest soul so she puts a plan into action
She gives a fairy tale to Leaf, the one of the many children of Shub-Niggurath (Baphomet), likely due to her unique talent and the power of "change" which sshe uniquely possess.
Becoming obsessed with fairy tales and their authors, Leaf wants something more, she wants to make her own story, and she also likely wants to include her authors within it. She basically wanted to make fan fiction but unlike normal fans, Leaf was a bonafide god, he could make this fan fiction real.
On another side, The Crawling One (Nyarlathotep) somehow ends up on earth, and witnesses the romance of Lewis Caroll and Alice.
There is not specific mention of Lewis actually fucking alice, just that they might've been a little too close than normal student and teacher. The Dean naturally noticed this and seperated them. After a long time, Alice Hargreaves invites her new teacher to a party. Upon arriving there, he sees alice, but not his Alice, not the young and beautiful girl but a hag who has already married another man.
Completely shocked and betrayed, Lewis runs out, wishing that he could have his alice. 2 gods hear of this, Leaf and TCO, the latter of which ends up granting him that wish
Wonderland
Lewis (there is a possibility of this being grimm, basically leaf made grimm, then was stolen by TCO, who granted lewis' wish, and likely dominated grimm's personality for a little while)
Lewis, Alice, and the prayer master have tea parties and enjoy piece in wonderland, however, it's not all peaceful, Lewis and Alice become closer, too close for the prayer master's liking. Out of jealosy, he wishes for something to change, and this wish reaches the ears of someone with other plans. Mary Sue, finally finding out where her favorite author went 'invades' Wonderland and connects her garden, The lost Empire to it, creating a twisted game of her liking, and creating her magnum opus, Grimm.
TCO notices this, after all, it's making changes to its garden, and also killing its aspect (prickett). However, it decides to simply watch, especially after the masterpiece that Mary sue creates, which intruiges, but mind you, she is always watching (ending d, wonderland top left next to jabberwock, she's in the top right corner)
(a small note, after consideration i don't believe that Alice at this point is likely prickett, who tries to help Grimm after mary sue invades and steals wonderland, so TCO isnt obsesssed with grimm yet. Based on mabel'ss dialogue this rings true as she talks as if TCO only went insane during it's play in BS2.)
Black souls 1
The twisted game begins, Mary starts writing however she wishes, playing a game of endless adventure with Grimm and the tales of the authors which make up grimm.
It's unlikely that grimm kept his memories after each cycle, but possbility of instinct remaining isnt far fetched (grimm recalls ending c in bs 2 despite it being over tens of cycle of ago and having hiss memory wiped multiple time)
However, his strength remained, and it kept growing, allowing him to get all the fairy taless, and see the real mastermind, mary sue, who delightfully confessess her misdeads.
He defeats her, and becomes a "god" of the world. However, even an ending in which she is defeated is still an ending, one which entertains the real 'god'.
Going back to zero once again, perhaps grimm could tell something was deeply wrong at this point, his hatered remained to some extent as after ending c if you interact with leaf, he stares at her a bit too intensely, a reason even he doesn't know.
He finds about Shub, who was summoned by Glinda, Dorothy's former apprentice. Being a possible lead, he follows the black trial and baphomet, curiouss where it leads him.
Ending D ensues, you beat baphomet, who in pure indignance can't accept that, and begs leaf to let her out, leaf doesn't accept this however. At this point though, TCO has had enough, it had seen everything, it was never unable to interfere, it simply chose not to. It likely acted because of 2 reasons.
1. As much of a child Leaf is, she is a genius, her power of change is phenomenal, and with it sshe created grimm, an amelgamation of several souls into one, with potential to rival The Great and Old ones in power, even surpasss the, aswell as the ability to breed other Great ones.
It is likely at this point or somewhere along the line that TCO actually absorbed alice, altough the timing itself just needs to be after the eventss of black souls in order to prevent timeline plot holes.
Black souls 2
Like all Great and Old ones, TCO was in its own way interested in humans and grimm putting his usefuleness for the war aside, it too wanted to 'feel' and thus it created a game with the help of Node (Or Nodens)
(note, im not quite sure why node did this, bs heavily follows Lovecraft's writings, yeah sure, none of the gods ever fall in love with an undead being there either but node being of assistance to TCO here doesnt make alot of sense here, since they are enemies)
Anyways, im ssick of writing so summary;
Same thing happends, grimm realizesss there's a problem with the new place he's in (thought he doesnt remember that much at this point)
This is what happened along the cycless(cannonical number was 60 something i cant recall, in node's notebook)
fell in love with Grimm
Tco became obsessed with grimm
Other old and great ones were invited to wonderland, who have come to know the masterpiece that is Grimm
Node asks mabel (Yog-Sothoth) for help in helping grimm escape. Mabel initially rejects the idea, however she changes her mind, and suggests a plan that's to node's benefit, that is, turning Grimm into a creator, using Grand guignol. (mabel's motive is to prevent the war between the great ones, as it will wake up The Idiot, or azathoth, while node's motive was being grimm's one and only supporter)
Node also brings in prickett on her plans
Wonderland becomes quite famous due to the spectacle that TCO is pulling, the great 4 elemental old ones however arent quite keen on joining, they prevent their followers, children and likely allies from joining, Kuti however doesn't follow this instruction.
Anyways, the new cycle begins, this time however, mabel and her garden. the chaos dungeon is there. This will allow grimm to grow much stronger.
(If you're curious as to why TCO never stopped mabel, it likely couldn't yog is practically THE old one 2nd only to azatoth, stopping it was practically unlikely. Though in the end, grimm becoming stronger was benefical to it, even if it became stronger than TCO, grimm was still in love with his darling alice, someone he'd never harm right?)
Also, ending G is initiated, grimm discovers red hood, and journey's through the mad world with some real sanity
(if you werent aware, sen isnt sanity, it's sendam is the full name, reverse that and you got madness)
Grimm recovers the memories of Lewis and his past (the hotel scene).
Grimm 'reaches the end' of the story once again, and starts another cycle, but with more clarity, he knows who this is, Alice Liddel, or rather, The Crawling One
Ending G happends (also likely ending F at some point?), however, Grand guignol is a thing, grimm can never escape as long as it exists.
Grimm remains ignorant of how he can actually escape, that is until finds a certain door which he cant open, advising him to go into the chaos dungeon.
Beating the old king, Mabel honestly tells about her plans of making him into a creator, aswell as showing interest in what he will do.
you know the drill, grimm discovers the graveyard and winterbell, goes through the mansion and recovers more of his past.
(it also has strange lore implications, there is an 'audio' log of lewis' interregation after he 'killed' the 3 sisters. Also GG is the one who keeps giving you hints. Though i havent seen it personally, apperently you can get some interview with leaf where she explain the mansion itself was a torture chamber for lewis meant to degrade him mentally)
He goess down the stairs with mabel, who educates him more on the situation that's happening outside.
Then her death scene happends, she "betrays" him to ease the suffering her death would've normally caused (altough, betrayal hurts plenty aswell, so im honestly not sure if that was the best solution) and Mabel is killed by GG.
First, Mabel isn't dead, well, not really, YOG isn't dead, but mabel is, she is simply an avatar of yog, so if you liked her, there is a possiblity of her coming back
secondly, GG killed mabel for 2 reasons, 1, she made grimm stronger than he needed to be, preventing fusion, and 2, she told him far too much
thirdly, Mabel feels feelings for the first time
This is my headcannon about the situation, so you can ignore it as it isnt the actual lore breakdown, just some food for thought.
I think mabel let herself die. Out of the 3 people who love grimm, 2 of them tried to manipulate him, and prickett is honestly an outlier
I think mabel didn't want to become obsessed like TCO and Node did, simply wishing to die with this 'pure' emotion of affection and love.
Anyways, you go down the stairs, meet the playwright (he's the original writer of the actual theater play also called Grand guignol, somehow out of sheere anger for being plagerized and jealousy for not being the one chosen by GG, he somehow entered winterbell and tried to stop grimm.
You know the drill, you either let yourself become one with GG, becoming a new creator, and node supporting you as your only beloved in the war, or you win, take the power of creation for yourself, TCO tries to stop you, but node holds her back while prickett helps you out of the garden as you and red hood escape.
And as you know, (i forgot to write about it) Mary's curse still takes place despite it happening in the previous cycle, and red hood dies.
Anyone's free to correct me, though this should be true