Greetings to all remaining and returning readers and fans, I hope you all have been weathering these current times as well as any of us can. It is with mixed emotions that I have composed what is likely the final update to a long declining fanfiction project. While I am still proud of this strange crossover story that sprang from my mind, touched by the warm reception it has received and feel my overall skills as a writer were bolstered by the experience of creating it, irl factors are motivating me to provide a final end to the story left hanging, and to some extent I feel self-conscious and critical of my story for perhaps bloating and expanding away from the core plan, becoming overly ambitious with the crossover factors.
Still, what's written has been written, and because I no longer feel the concise episode summary format is working the further ahead I get of the planned plot I want to simply brute force the explanation of this tale here, and hopefully provide readers with some sort of satisfying, formal conclusion, as rambling and composited as it might be. As fittingly ironic as it might be for a fanfic series inspired by spite for unsatisfying endings to bloat up and peter out itself on a dull note, I hope you all enjoy the read below and the story as a whole. Thank you for your time and feedback, everyone.
I guess off the top I'll admit I hadn't entirely thought out how The Owl House and Amphibia really fit into the actual narrative of this story because I was far too enamored with how well they fit into the shared setting I was linking together. As everything fell into place however and those shows continued their plotlines it became more complicated to make the pieces fit, since the actual narrative of this work is primarily woven through the characters of Gravity Falls (Part 1), Star Vs (Part 2) and Steven Universe (Part 3). I feel unsatisfied by the inclusion of the superfluous extra settings because I feel they have overly complicated the dimensional structure I've world built and essentially reduce the very interesting worlds of those shows into battlegrounds between Bill and his enemies. Below are truncated summaries of how I suppose these could be stuck together into a coherent plot, and a few other ideas that were likely destined for the cutting room floor.
Everything ahead is going to be presented by subplot but in execution would have all been happening in parallel over the unmade chapters, with some characters assigned to specific subplots while others float around more freely. Consider it all as canon or non-canon to the AU as you wish. As always, I grant full permission to anyone who wants to make use of these ideas for their own fanfic.
War of Amphibia
As a political allegory in the context of this story, the dimension of Amphibia represents the wild frontier and exotic lands inhabited lower technology "primitive" cultures. If the Lucitors were able to defeat the Butterflies entirely and cement their rule over the dimension of Mewni according to their plans, Amphibia is the kind of dimension their new Empire would seek to colonize and brutally exploit for resources. Fortunately for Amphibia they're "only"currently dealing with Bill's personal army due to Mewni being hermetically sealed, but that's still quite enough to wreck a bloody reign of terror over its population.
Unfortunately the extremely difficult environment and the fact that Bill's soldiers are local bandits and raiders gathered under his flag means the Coalition resorts to some dangerous things to dig them out and secure the Calamity Box.
Ideas I had included: Non-royal Mewmans being given concentrated magic cocktails to induce temporary Golden Butterfly transformations so they can go on bombing runs over the jungles. Dedicated flamethrower robots being produced by the factory the Coalition operates. Dipper forming new friendships with the lost girls Anna/Sasha/Marcy while struggling to not let his hatred for Bill Cipher cloud his judgement. Mina Loveberry is put back into action on this campaign front and very quickly goes all Heart of Darkness on the natives, forcing Star to put her old idol down like an animal and further straining things between her and Moon.
None of this is really improving Amphibia's perception of the terrible human beasts unfortunately, and it ultimately costs the Coalition the Calamity Box: An idea I had was that Bill takes a bunch of civilians hostage, along with Marcy, and demands the Box be exchanged for their safe return. The Pines adamantly refuse to negotiate with Bill but a Wartwood angry mob just steals the Box and the mayor hands it over. Naturally Bill doesn't keep his word, and while he doesn't have the jewels to power the Calamity Box up conventionally, by harvesting some of his Homeworld Gem attaché staff and shoving their Gems into the ill-fitting spaces on the Box Bill is able to accomplish a single emergency dimensional shift to return to the Homeworld when the tactical situation turns against him: After Bill double crossed them by killing all the hostages the inhabitants of Amphibia flatly resent both sides (save for some outliers, naturally) and the Coalition have to fight a grinding battle to finally push them back, even after their Grand Druid jumps ship.
By the end of things the Coalition are on the verge of defeating Bill's legion when something dire happens, the marking point between the end of part two and into three which affects all other running plotlines: The Underworld has successfully reversed the polarity of the bubble Hekapoo placed around their dimension and now control it from the fortress they've built atop the MHC Sanctuary. Bill and the Lucitor Royal family now have full control over who comes and goes from the dimension of Mewni and turn the final push into a route with the arrival of Hellknight reinforcements. The headquarters Bill had established in his druid character becomes the beachhead of an Imperial colony funneling resources back to Mewni for the duration of the Lucitor's reign, though the damage from the previous war handicaps its rate of expansion and it never becomes a significant target.
The natives of Amphibia have been depleted of their enthusiasm for war at this point and broadly refuse further cooperation with the humans, though of course individual exceptions exist: A number of amphibians still believe the Lucitors are a threat and continually stage small scale disruptions on their colony, while other are intrigued enough by their glimpses of the human world to visit Gravity Falls by way of the restored robot factory, which the Pines have kept running and equipped with a portal setup. The remaining toads loyal to Captain Grimes and many of these visitors recruited by Sasha form a sort of foreign legion to the Pines-Butterfly Coalition, giving them some professional soldiers beyond Mewni's surviving knights.
The Hexside Incident
At this point in the story Mabel is essentially the Pines-Butterfly coalition ambassador to the Boiling Isles, after the Queens signed the agreement and returned to earthand is pretty good at it. In addition to relaying scrying intelligence and negotiating small exchanges between the Coven and the Mystery Shack, Mabel is acquainting herself favorably with the Hexside students and even learning a spot of magic herself.
The last two are both made easier by the literal fruit of Eclipsa's research; A rapidly flowering magic absorbent plant that collects energy from the environment around it into a bulb that be plucked off and eaten. Besides being delicious, the rainbow juice fruit makes humans temporarily capable of magic use (in a fairly twitchy, chaotic sort of casting that isn't always predictable) but operates as a focus agent when ingested by witches. Dipper has refining the substance into something that can be taken on missions as one of his ever growing number of science projects, but fruit juice gum candies are good enough to get popular in Hexside.
The imprisoned Bill fragment is slated for execution on Grom Night, and while Mabel did have a date for the dance by this point in the story she's mature enough to go deal with Bill despite this since no one else is available though she does try and rush to get to the party afterwards.
Ironically this makes it difficult for Bill to try and psyche her out to save himself since she's urging Lilith and the Imperial Mages to hurry the execution along, but ultimately Mabel lacks the arcane knowledge to spot the modifications Belos has made to the rune system: In addition to producing a counter-wavelength magical charge into Bill's prison crystal ball to destroy the fragment, a secondary rune system produces a fragile copy of Bill's psychic impression and broadcasts it into the actual Grom Night monster, causing it to take Bill's appearance as one of its many forms during the fight.
Belos does this to create fear of an outside enemy in Bill Cipher and the Lucitors who worship him in order to increase the appeal of the Imperial Coven, but this was ultimately a misstep: The image this creates of Bill outside the carefully rune warded Imperial prison gives the real Bill fragments a fleeting glance into the Boiling Isles... and he is immediately interested in Luz, who is in turn one of the few people in Hexside who is already suspicious of Mabel, under the impression she's a Coven spook who has been digging a lot into Eda's background.
The night after the annual celebration, Luz begins to have strange dreams...
There were two other ideas I had for comparatively more lighthearted "episodes" happening before the end events of Owl House Season 1 would get covered: One is about a gaggle of Hexside students going on a doomed educational field trip being held as a special collaboration project between the Coven and its allies, hosted by Lilith and Stanford.
Unfortunately when the date comes Stanford happens to be in space so Stanley has to fill in for him, resulting in a disastrous black comedy Magic SchoolBus parody where an attempt to visit a fascinating dimensional abnormality (something like a cluster point where all sorts of lost trash and black hole consumed matter rematerializes) that gets even worse when the students run afoul of an outpost of Lucitor Abyss Whalers constructed nearby, get taken hostage and all have to work together to escape. They don't learn much about magic, but the students do gain a valuable lesson about trust, pickpocketing, and the importance of not hunting magic dimension whales into extinction for their bones and blood. Most of them also develop a fear/hatred of Lucitor soldiers after nearly being killed by them as well as an early taste of combat trauma... exactly as Belos had planned when he discovered the existence of the far flung whaling station via scrying.
The B-plot to this story concerns Luz, who could not go on the field trip due to not having a signed permission slip, taking the opportunity to break into Mabel's embassy space and snoop around. They do not meet face to face but some intriguing parallels are made by Luz going through the other girl's stuff, both for the characters and the audience: Luz has a sort of muted blend of the twin's individual strengths (she's not as wild in the imagination as Mabel or as intuitively brilliant with magic as Dipper) while not being as afflicted as strongly by their related personality flaws.
Anyways Luz figures out quite a lot from her snooping, including the fact that Mabel has also been snooping around and has accumulated a lot of data on Eda, Lilith and Luz herself, along with Mabel being definitively human (officially, everyone from the Coalition introduces themselves as Mewman on the Boiling Isles) and responsible for the introduction of the Rainbow Gumdrops magic boosters that have been going around. All of this makes her increasingly suspicious of the ambassadors and more vulnerable to Bill Cipher's influence.
I had always wanted to work a little commentary on grudgby into the fic, with the joke being that grudgby is the multiverse-version of soccer while cornball, adored by mewmans and basically mewmans alone, is American football, wasn't sure where to weave it in though.
Agony of the Witch more or less pops off as canon and Mabel is forced to manage the political upheaval it might cause with their ally alone, as she's the only Coalition-member on the Boiling Isles when it goes down.
When Luz is first captured in the Imperial Castle she has a personal visit from Mabel, wherein Mabel offers Luz a deal to return to earth and tries to apply the information she got out of several conversations with Amity, while Luz drops the revelation that she figured out the Pines she's encountered are all human but refuses to trust Mabel and sees her offer as insincere.
Things are falling into place for the Pines, and she leaves the meeting both impressed and shaken by Luz's obvious confidence that Eda will appear and rescue her, even if it's a bit of a facade atop legitimate worries she refuses to show while being interrogated. Mabel attends the duel between Lilith and Eda as a result, and it all adds up.
The duel ends, Luz escapes to the Owl House as canon but here, Belos has a better plan than telling Lilith to her face he never intended to cure her sister: Instead he's simply going to kill Eda in her cell and frame it as suicide. I like the mental picture of the Emperor's tiny advisor Kiki walking to the witch's cell to do the deed with an earth import revolver that's clearly too big for her.
Fortunately Mabel is around as an alternative source for Lilith's moral epiphany, and as soon as she can get Lilith alone Mabel lays into her for being a selfish, controlling sibling whose solipsistic thought process means she's actually ruining Eda's life instead of improving it. The conversation starts as a shouting match, but the uncomfortable sincerity of Mabel's arguments and the obvious grief and regret that come bubbling up with it strike a cord in Lilith, and it gets broke down for her why exactly she's wrong by someone who made the exact same mistakes as her:
Lilith just wants to get her sister back, and isn't truly thinking about how to actually help her get better. Rather than admitting to her selfish, pointless mistake in cursing Eda she simply buried the truth and made all the decisions about how to cure Eda by herself, acting like it's exclusively her right to decide how her sibling's future unfolds despite being the one who is actively ruining it and doing so in a selfish way that detaches Lilith from responsibility for her own wrongdoing.
Anger turns into guilt and legitimate sympathy halfway through the conversation though, and Mabel tries to get it through to Lilith that even if she were to succeed she wouldn't have her sibling back, she'd just have a prisoner who'd be perfectly justified hating her forever! Mabel feels deeply humbled by just how bottomless Dipper's capacity to forgive and keep caring for her is, and she's legit scared that Lilith is going to completely deplete that capacity in Eda if she keeps acting so selfishly.
Mabel speaks directly from the heart on all this, as while she and Dipper have "formally" made up and forgiven each other in light of the massive scale the conflict with Bill has grown to she's still worried deep down that Dipper will resent/distrust her to some extent for the rest of their lives, but this cathartic outburst on Lilith helps Mabel accept the fact that she just has to live with that and strive to do better every day, not to try and "make" Dipper supportive of her again but because it's the right way to treat someone you love. And you just have to hope that they can still love you back, because they're under no obligation to do so.
This rocks Lilith to her core and pries at her existing doubts perfectly, and in a moment of mutual understanding Mabel Pines manages to redeem Lilith Clawthorne, conveniently in a way that keeps her political position inside the Imperial Coven intact!
The two selfish sisters rush to the dungeon to try and rescue Eda, but it's too late: The walls of the dungeon are blasted down by Luz, glowing yellow with power and sporting a third, all-seeing eye manifesting on her forehead. With the polarity of Mewni's containment bubble reversed Bill is able to forge a deal with Luz, giving her a temporary surge of raw magic power to bust Eda out of prison and sweep them (Luz, Eda, King, Hooty and the house itself) away to the "safety" of Mewni, where the witches are received as guests of the new Lucitor Empire.
As a result of all this the events of Owl House season 2 essentially don't happen. Mabel returns to earth as part of the coalition preparing for open conflict with Mewnibut stays in touch with Lilith, who is herself increasingly unsure about her place in the Imperial Coven but maintains her position in it, becoming a key connection in the Butterfly-Belos alliance.
On Mewni, Luz and company are being wined and dined by the Lucitor family, receive royal medical treatment for Eda's curse and are generally won over by the Underworld's rhetoric, at least until they start encountering Bill's atrocities first hand: As they have it explained to them Mewni and her Queens were a bunch of corrupt, genocidal imperialists that the Lucitors led a revolt against and overthrew. Now, under the divine guidance of Bill Cipher, the Underworld is working to redistribute the magic Mewni hoarded for the good of all and carry the torch of liberation into the wider multiverse.
Similar to Belos and his Imperial Coven being villainous allies to the protagonists, the cast of the Owl House would become morally heroic characters manipulated into fighting for Bill Cipher. Since the planning for this stage is very broad and general though you'll just have to imagine what matchups end up forming, though more Luz vs Star magic battles would have to happen if I was writing it all out. More information on how Nightmare Mewni would begin attacking other dimensions is the start of Part 3.
Alien Elite
As the war against Bill is dragging on across the multiverse, Ford eventually cracks open the alien containment unit he took from the crashed ship and buried in a graveyard. He and McGucket are carrying out the examination at the Northwest Manor, which is increasingly being converted into a control center/laboratory away from the Mystery Shack. Inside the crate is a shriveled green corpse and an inert box of alien electronics: This is the Invader Zim himself, seemingly dead in a box an entire dimension away from the Irken Empire.
McGucket hooks up the alien's PAK to the mansion's new computer system while Stanford handles the dissection, and from this study a great deal is revealed about the Irken Empire and their rivals in space, the Diamond Authority, albeit from an acknowledged as biased perspective.
As an honest confession this is where I was beginning to wonder if I'd branched too far and made the whole story far more complicated than it needed to be by establishing the galactic war are happening in its own dimension instead of just in space early on and then sticking to it, but it eventually worked out into the rough ideas for a story below. Who knows how it would have been in execution of course.
When a Bill fragment was tossed into the multiverse and into the interstellar war he eventually took advantage of, his first pick for patsies was actually the Irkens, but as stated previously they simply used the first dimensions corridor they built with his guidance to get rid of Zim and then destroyed it to trap him there, causing Bill to go to the Diamond Authority.
What is important is what Zim's mission was here: The Tallest spun him an elaborate yarn about the Empire having constructed a rudimentary time machine, and they want to send Zim through it on a special invasion mission that needs the most special Invader to accomplish it: Invade the Gem Homeworld eons in the past and destroy them before they can become a prominent obstacle to Impending Doom.
Zim was naturally incredibly excited for his great mission and obeys eagerly, but his glory seeking tendency to "improve" on his orders and equipment leads to him tinkering with the dimensional gate and giving it ACTUAL time travel capabilities. Zim ends up going exactly where he thought he was being sent, but in the wrong timeline to benefit the Irken Empire he fights to accomplish it for; Deep in space away from the "main" earth of this AU's timeline, geological ages in the past.
He did not reach the Gem Homeworld so early in it's history that Zim could just walk around breaking geodes to halt their evolution, or however this species came to be, and is instead captured by Era 1 colonization spaceships. Half a prisoner and half a curiosity, the Invader is shuffled around and experimented on for several decades until chance brings him face to face with Pink Diamond, well before she discovered the planet earth.
The isolated would be ruler finds the cyborg alien invader oddly compelling to talk to, seeing Zim as a small and funny sort of version of her immediate family, which is the angle Zim works his plan through. He steadily builds a trust in Pink Diamond as her favorite of the curiosities she keeps in her organic zoos until he's able to convince her of a plan that they can do together: A plan to poof the other three Diamonds in an untraceable accident, so that Pink can take control of the Authority in their steed, and then they'll all see how amazing she is at it when they regenerate!
Zim is manipulating Pink the entire time, naturally, and instead of incapacitating the other Diamonds he simply assassinates them, using Pink's security clearance to sabotage their personal starships into flying into black holes or simply exploding during takeoff. The Diamond Authority immediately crumbles into anarchy and civil war as Pink proves to be a terrible ruler, completely shattering the religious illusion of superiority the Diamonds built to idolize themselves. She eventually exiles herself to this timeline's version of her private play garden to descend into depression over her failure, while Zim's attempt to escape the assassination by hijacking a Gem scout ship goes badly, resulting in the saucer crashing into Gravity Falls and discovering earth (not that there is an Authority to colonize it anymore) and creating the wreckage Stanford would eventually unearth.
So in the reality this AU has been "based" in so far the Gem species went extinct eons ago and the cosmos above is a much more peaceful place for it. Zim's organic body is thoroughly dead after the ages of ill-fitting hibernation and being actively dissected by the Pines, but I had an "episode" idea where his PAK is still alive and makes an escape attempt through a window of opportunity opened up by all the data mining the Coalition is doing to it, skittering across the town while killing and maiming in order to reach the Mystery Shack portal and hack it to transmit "Mission Accomplished!" to the Tallest.
This data does prove worth the cost of stopping it however, as when Mewni reverse polarizes itself to become a beachhead of the Nightmare Realm the only possible way to access it is with the Calamity Box, which is now on the thriving Gem Homeworld of the other timeline. And so the dark fantasy thriller steps up into a space opera...
The last hurrah of the old, Gravity Falls inspired way of doing things would be a few dark comedy road trip chapters where Ford reaches the Godzilla Threshold and calls for an old associate he didn't want involved in the Coalition: Rick Sanchez. Unfortunately they need his extremely technological capability to cross the galaxies and investigate Pink Diamond's final resting place, since Zim's PAK records indicate she had the means to subvert ALL the Homeworld's security technology.
So Rick and Morty along with Stanford and Dipper have a few whacky adventures traveling across space, having brief cameo crossovers and stopping to refuel on whacky planets full of life, where the conquering jewels from the edge of the galaxy are ancient myths no one believes in. They get to the garden planet and discover Pink Diamond eventually shattered herself in the depressed isolation of the place, having come to believe that everything the other Diamonds said about her was completely correct and that she got them all killed. Stanford scopes up her remains after the four of them potentially fight and shatter this timeline's incredibly insane versions of Spinel and Pearl, who have become full on grieving spirits, essentially, and take Pink's fragments back to earth, where careful examination goes on to give them a lot of information about the Gem species, now that they can compare the structure of a Diamond to that of an expendable lower class Gem.
For it's emotional crux, this last hurrah also helps Stanford achieve a bit of perspective: He finds Rick to be way more objectionable than he remembers from when he was lost in the multiverse and is particularly appalled by how badly he treats Morty. The meeting of these four for this adventure would serve to contrast Ford's well meaning education of Dipper against the Rick and Morty dynamic, lighten up Stanford's perception of Stanley (he's a crook a lot like Rick but he's far more sincerely devoted to the wellbeing of his family) and explain why Ford doesn't try and pull his old smuggling contact into the war against Bill, given how crazy dangerous Rick is at overthrowing galactic superpowers.
From that point on there is nowhere to go but onward into the timeline ravaged by intergalactic war. Our heroes face their most dangerous battles yet...
So, yeah, hope that wasn't all to awkward/underwhelming to read. I will be posting one more chapter detailing what was planned for the science-fantasy space opera that was Part 3 to this AU trilogy, along with character endings and lingering answers, when it is compiled to my satisfaction, and that will mark the final end of this firmly out of control, over-ambitious fanfic universe.
To all the enthusiasts who have stuck to this story this long, through the fleeting highs and gaping lows it has experienced, I can only thank you sincerely and hope the wait continues to be worth it. If you have any questions, ideas or outrages you want to field in the reviews section then by all means; I will do my best to answer/discuss them in the final chapter.
Stay safe out there to everyone, and try to do your best to make the world a better place, even just a little.