Chapter Text
The basic premise runs as so: RWBY, JNPR, and CFVY are flung into 3 separate alternative universes, and find themselves caught in a plot that spans the entire multiverse, with all of reality at stake.
Team RWBY is thrown into the ancient times of Remnant, where Salem and Ozma are still young, but the Magier kingdom has fallen. Remnant is lawless, and Team RWBY dedicate themselves to saving as many people as they can in a lawless, but now prospering Remnant.
Then comes the Reapers, a species of interdimensional creatures, neither good nor bad, but simply neutral, that travel across all of reality, dispensing mortality to all of the species that they come across, and perpetuating existence through the cycle of life and death.
RWBY becomes dedicated to stopping the Reapers, and making sure that Remnant survives, but along the way...
They overstep. They screw up. They do something disastrous.
What that disastrous incident that they screw up at even is, I don't know. I haven't figured that part out yet (Maybe something to do with Ozma and Salem, maybe an alternate Team STRQ or Summer Rose, but what matters is that it happens, and RWBY begins to step down a dark path. A righteous path, yes, and a well-intentioned path indeed, but a dark path indeed.
They become dead set on stopping the Reapers, and making sure that, now, and forever, life would always prevail.
Elsewhere in the multiverse, Team JNPR would find themselves in a world where the Grimm were coloured a pure white with blue eyes, and the Magier kingdom never fell, with Salem and Ozma becoming ruthless tyrants over a world spanning empire. Teaming up with this world's equivalent of the White Fang, as well as the Grimm, led by the Mind of Grey, a Grimm so old it had become sentient, and as such had grown tired of mindless destruction, and as such, now sought only the continuation of creation, Team JNPR would dedicate themselves to overthrowing the Magier kingdom, and eventually would, becoming fused with White Grimm in the process, and becoming pure human and Grimm hybrids.
However, along the way, Team JNPR discovered the existence of the Reapers as well, and found that Salem and Ozma were attempting to fuse themselves with the power of their power, and in a climatic showdown, they are able to defeat the both of them, and banish their spirits away into the multiverse, where they would look through, and see something terrible.
All of creation becoming undone. Monsters going on forever. The Reapers kneeling over and dying. The balance of life and death, reduced to ashes.
And Salem and Ozma, slaves to a new evil.
Team RWBY.
Horrified at what they saw, Team JNPR move to stop the coming calamity that may destroy all of existence, and with the help of the White Grimm and the White Fang, they move through the interdimensional cracks, towards where this is all starting from.
The centre of the universe.
Remnant, during the Dark Times.
And finally, elsewhere, Team CVFY find themselves in a lawless future Remnant, where the kingdoms have collapsed and mankind is reduced to a scattered few million across the globe. Taking up jobs as bounty hunters and mercenaries, they come across a child, and come to a startling realisation.
This child looks exactly like baby Ruby Rose.
The team travels around the world with this child, following a breadcrumb of a quest left behind for them to follow, and pursued by mindless Grimm and other bounty hunters all of the way, until they reach the end, on the island that was once known as Patch, where they discover the person who had been hiring all of the hunters to go after them, controlling the Grimm, and had been hunting them down for so long.
Yang Xiao Long. Their Yang Xiao Long. The same Yang Xiao Long whom they had gone to school with, and whom was now demanding that they hand over the baby.
A chaotic fight ensues, and in the process, the Reapers, somehow under the weak control of Yang, flood into the world and attack Team CFVY. Fearing for their lives, the team, still holding the baby, jump through the interdimensional crack, and find themselves at the centre of the universe, on a Remnant, far into the past, far into the Dark Times. The times for Beacon where there were no kingdoms, and mankind was barely just clinging onto life by a few million.
Team CFVY and baby Ruby meet up with Team JNPR and their allies, and they come to a startling realisation: The baby Ruby that they had with them is actually an infant Reaper! Every single Reaper in the universe is a copy of Ruby Rose, and they're all dying.
A jump cut to Team RWBY reveals what had happened and what was going on: Hitching a ride onto the spirits of Salem and Ozma, they arrived at the centre of the universe, where they found the Prime Reaper, Ruby Rose- The one from the canon anime. The details of how she got to this point are best left unaddressed, but what happens afterwards is the most important.
The 4 of them kill this Ruby Rose, and their Ruby, and the rest of them, take control of the Reaper race, thanks to the hybridisation of Ozma and Salem, and use them to end death around the universe forever, making sure that life will always win.
However, this has greatly upset the balance of the universe, and all of creation is coming undone.
Realising that what Team RWBY is planning could spell the doom of all of creation itself, Team JNPR and CFVY hatch together a plan, and a big climatic battle ensues.
In the ensuing final fight, Team RWBY is defeated, but the Mind of Grey and the baby Ruby Rose are fused together in the process, becoming the next Prime Reaper, and ensuring that creation may return to normal, and may continue on yet again.
All of reality is saved, story end.
What happens in the aftermath is up to you.