All Pokemons have the possibility (even if technically impossible), to become Mew. This possibility allowed for the first Mew to have such an existence (Risa) and now there's a second.
***
Location - America
Time - A few days ago.
"Did they seal Glitch here?" Snow the shiny Mew thought.
When Mike had asked her which Pokemon she wished to reincarnate into he never expected her to choose Mew and was strongly against it too.
Limit breaking and Mew are exceptionally difficult. This is what he believes when so far Mike had only seen 1 Mew who can access Origin without entering transforming. Progenitor Mew.
Risa had somewhat broken that rule by using Hidden Power: Origin, but that doesn't fully count as accessing Origin.
That's why Mike was highly against her being one, but with her being adamant at this and the fact Mid-Divine was the best she could've gotten who would've still needed to limit break, he let her be.
Being strong isn't all that is needed of one and Origin isn't needed to free Glitch.
It didn't take Snow long to find the Pocket Dimension and being a Mew, Unowns didn't care one bit of her existence unless she intervenes in their sealing or unless she's an ERROR.
Inside this dimension, Snow's eyes widen in shock. This place compare to what was illustrated to her by Mike is far more difficult than the previous one.
It didn't make it any better that her current strength is inferior to Mike's at that time.
However, there's one thing she has that Mike didn't have.
Anger.
Snow is the Pokemon he invested in when reincarnating her, making sure her Wrathful Devil was upgraded to something far more destructive.
#Wrathful Devil: Satan#
This makes it so her anger makes her strength rise significantly, it would even grow to the point where it can ignore laws and type effects.
If she were to fight Mike of that time and last long enough, she would sooner or later overrun him with sheer power.
Together with her Snow's now, Elementalist themed fighting style, the wave tactics of Unowns were futile against her.
The Anti-Army Specialist, Snow.
...
Time - Present
After a few days of slaughtering, Snow had finally wiped them out and can now focus on Glitch.
However, time is short and the chains wrapped around Glitch are far stronger than the one's seen last time, but...
*shatter*
"Let's go," Glitch effortlessly glitch everything that made those chains special and broke free, leaving Snow to stand there aghast.
"Hehe, don't let honey know," Glitch smirks.
As annoying as those chains are, for Glitch no matter how many anti Glitch, ERROR, or energy they slap onto it, she'll eventually break out from it. Unowns have long since been aware of this and that's why they would always be enough inside, enough to stall her long enough to seal Pocket Dimension thereby sealing her and finally putting the Pocket Dimension inside a Pocket Dimension.
The only issue with this loop is that it doesn't calculate outside variables.
The Unowns didn't react to Snow as heavily as they should've and due to this, Glitch is now free.
Similarly, back then when Mike was trying to free her, she could've freed herself if she wanted to. However, how could she interrupt her white knight?
"Let's go!"
This shall forever remain a secret, one of the soon-to-be many secrets kept from Mike.
...
Location - Viridian Forest
"This isn't good," Marshadow muttered.
"I'll save them!" 'Pink' waves her hand unleashing cursed flames that rushed towards Marshadow.
In this dark plane, Shadow monsters of all shapes and sizes rushed towards 'Pink' each equipped with the Origin of Marshadow, yet surprisingly they were swallowed and devoured by the Curse Flames of 'Pink'.
'Origin' Marshadow thought in shock. 'How did she break her limits this fast, how did she grow and understand herself in a month,'
#Origin Hyper Voice#
'Pink' mouth released a powerful sound wave destroying this plane before rushing towards Marshadow.
"You're still too weak!" Marshadow shouts materializing her lance. Thanks to 'Pink's unbelievable talent, Marshadow couldn't allow her to leave.
Now she needed to not just beat her here but somehow shatter or seal her Origin.
'Pink' awakening Origin wasn't a part of the plan.
...
Location - Pocket Dimenison.
"So much for weakening them," Necrozma mocks, in hand was the Draco Plate. "They all have grown beyond what you can handle,"
Using the energy within the Draco Plate, countless meteors descending all aimed at Arceus.
"What can they do with their pitiful strength?" Arceus mocks. "You should be more worried about when Ouroboros escapes my clutches,"
Ouroboros has already grown to rapidly, Arceus is even consider sending Celebi to aid them. It has only been so long since she broke through a limit and now with the aid of limitless she'll do it again. Either she'll be equal to or even surpass Regigigas after this.
#Air Slash#
Boosted by the Sky Plate and Space-Time Plate all the meteors in the sky were split in two.
"Let's start the first Check," Arceus said. The runes that originally cover this Pocket Dimension thanks to Adam shone brilliantly as Arceus took control of them all.
#Brilliant Diamond and Shining Pearl#
Space and Time began to bend as each rune changed into one type. Explosion.
Arceus' figure escapes this Pocket Dimension just as it was sealed and imploded.
Standing outside it and looking at the water-concealed crater Arceus, awaited the survived Necrozma.
"Piece of sh*t!" Necrozma growls destroying the Draco Plate in hand. "The world can die with you,"
With the Pocket Dimension gone, the rules Arceus had implanted are gone.
#Star Strike#
It was a horrifying sight to see the stars in the sky, gather all together, merging into one enormous sun and finally seeing that beam of energy that was further enhanced by Necrozma coming down at earth.
"Suicidal," Arceus muttered, that would've gone straight inside the crater, broken through the barrier and damage the core.
WOULD'VE, but as the attack went inside the crater, the creater absorbed all the energy instantly.
"Did you gather all the stars for that pitiful attack? Regarthless, let's send it back at you and seeing as I'm generous. Let's send it back as Dark-type energy,"