Honestly, I had a wacky dream the other night. It was a daydream but that should still count.
vs
This was an epic fight between Marshadow and Hoopa which more so became an adventure about how Marshadow went through step by step processes in order to win.
This fight started off with Hoopa being well-aware of its x4 weakness to Ghost so it left off while being chased by Marshadow. As this chase was happening, Marshadow would be warped through various portals, fighting off against various legendary and mythical bosses. Hoopa was shifting on and off between formes but mostly kept its bound (regular).
I had lots of different variations of this daydream but I'll explain the one I followed through most with.
After a while into the fight with Marshadow and Hoopa going on a chase, the first notable boss Marshadow had to deal with was Mega Rayquaza. Mega Rayquaza first used Dragon Dance, then used Dragon Ascent. Right before Dragon Ascent hit, Marshadow fully set up a Substitute. Marshadow kept spamming Substitute until Mega Rayquaza's defenses were lowered enough for it to lose against Spectral Thief. After beating Mega Rayquaza, Marshadow went through the next portal. Marshadow got lucky and found a Full Restore somewhere inbetween travelling through this portal, then got transported to where it was alone in a world with Arceus. Marshadow used Bulk Up while Arceus used Shadow Claw. Knowing what was up next Arceus tried to use Extreme Speed, but failed. Marshadow used Close Combat and OHKOed the Arceus. Marshadow was then transported to a city, which was the climax of this fight.
Last Moment by Yousei Teikoku was playing. What Marshadow was witnessing, were massive windstorms, waves of distortions between time and space, and lots of downpour. As it turned out, Hoopa summoned Lugia, Kyogre, Groudon, Palkia, Dialga, Reshiram, Zekrom, and Kyurem by its side. They were all attacking the Marshadow and Marshadow was left only to constantly dodge all of those attacks. It encountered Dialga face to face, used Bulk Up, and one-shotted it with Close Combat, then found a bunch of regular Pokemon in the city it could get a hold of to join for its own aide. The regular Pokemon just kept getting demolished but they spared Marshadow some time. Entei, Raikou, and Suicune later appeared to help Marshadow out. When they arrived, Marshadow hopped on Entei, riding on it through the city. Volcanoes were erupting everywhere on top of the massive downpour and windstorm going on in the city. There also came a bit of thunder. Next, Marshadow pulled out a Rainbow Wing and summoned Ho-Oh. Its team of legendaries became Entei, Raikou, Suicune, and Ho-Oh vs Hoopa's myriad of mascots. The beasts did not last very long, as Palkia started going wild and erasing parts of the city from existence, including them. Ho-Oh was mostly fighting off against Lugia and trying its best to hold it back. Marshadow was still running through the city with everything behind its back. Primal Kyogre chased it with a small surf wave, then Primal Groudon chased it and spammed Precipice Blades. One of the Precipice Blade attacks ended up hitting a random Focus Sash Wobbuffet full on, so it used Counter and Primal Groudon got nuked. There was a massive explosion. Kyogre then took this as an advantage and started elevating the sea levels very high up. Reshiram got mad and burned parts of the city with all the power it had. It could not really do much due to all the water everywhere. When this happened, Zekrom and Kyurem decided to team up and do a fusion dance, turning into Black Kyurem. Black Kyurem then drew out as much power as it could and froze the whole world. Primal Kyogre was frozen. Reshiram was frozen. Ho-Oh was frozen. Lugia was not anywhere to be seen. Palkia was still moving but was somehow snapped from Hoopa's control and decided to leave soon after this moment. From how it looked, it was just Marshadow about to face Black Kyurem. Instead, multiple Ultra Wormholes opened up and what came out was 5 Lunala. They all pulled in separate moons from the Solar System onto the city, shattering much of the ice and world itself. One Solgaleo then came, flew in front of Marshadow, then let out a roar. This roar very suddenly launched the Sun into Earth like a baseball flying through a glass window after being harshly thrown. Marshadow went hiding under the shadows below and there was seemingly nothing left but pitch darkness...
Apparently right before Solgaleo threw the Sun onto Earth, another Ultra Wormhole appeared, but to the right. What came out was a very fast moving Necrozma, just trying to absorb the Sun. It was successful. After there was pitch black, Necrozma suddenly lit up like a candle and became exposed in its Ultra forme. A new fight was beginning. The light it brought out shined as bright as the Sun.
Ultra Necrozma's own theme was playing. It was given a +1 omniboost in stats and portraying itself as what could have been the final boss to Marshadow's adventure. All of Marshadow's stat boosts through Bulk Up and any previous stat-stealing were apparent and still applicable to this match. The fight begun.
During the beginning of Marshadow's fight against Ultra Necrozma, an Ultra Wormhole popped up somewhere near where the Sun originally was. A baby Arceus was thrown out of this Ultra Wormhole, with its only sight being pure darkness and some stars. The Baby Arceus was confused, bored and wanted to do something to get rid of this darkness.
Marshadow kept on facing the Ultra Necrozma, dodging its attacks and doing whatever it took to keep doing damage to it. This was mostly by spamming Spectral Thief.
In the middle of Marshadow's fight, baby Arceus's role became apparent. It was halfway towards creating a completely new Sun and giggling with glee like an infant. Marshadow noticed a new Sun was being recreated and needed to plan on finishing off Ultra Necrozma as quickly as it could. Ultra Necrozma then decided to unleash one big Light That Burns The Sky attack. Marshadow hid under the shadows below to dodge it.
The fight continued until baby Arceus finally completed a recreation of the Sun. Ultra Necrozma was greatly weakned and on the verge of losing. It looked up towards the sky, noticed this new Sun, and made an attempt at lunging as fast as possible towards it to regain all of its energy. Marshadow was not giving any chances. It outsped with +1 priority Shadow Sneak, hit Ultra Necrozma head on from the front, and took it down. As this was happening, the same Ultra Wormhole baby Arceus came out of opened up again, this time, spitting out a Uxie.
The Uxie was really confused as to why it was brought near the Sun next to a baby Arceus so it used Future Sight in order to see what was happening. Uxie very clearly saw and made a plan with the Arceus.
Ultra Necrozma's defeat gave Marshadow a Marshadium Z in hand. After the Necrozma disappeared, Marshadow found Hoopa again. Hoopa noticed and made another escape attempt. Both Marshadow and Hoopa kept going through portals in an all out chase.
Uxie brought out a whiteboard and showed Arceus a trick. It wanted Arceus to create a clear, wide platform on top of the Sun. The baby Arceus did just that. Afterwards, Uxie waved its arms up then down, and the Arceus was taught Gravity. Arceus then used Gravity. Uxie clapped, gave baby Arceus a pat, and fed it a treat.
After travelling through more dimensions, Hoopa decided to head to where the Sun was and Marshadow kept following. Hoopa made it, immediately spotted Uxie, then immediately threw Uxie off into some unknown location against its will. Hoopa then saw baby Arceus and wanted to spite it. It used up its psychic strength to lift the Sun and aim it towards Earth to repeat what Solgaleo did. Baby Arceus went off crying. Marshadow arrived, landed on the platform Arceus created and saw the baby Arceus crying. It was peeved. Marshadow took this opportunity to use up all of its anger and its Marshadium Z to unleash a Soul-Stealing 7-Star Strike Z-Move attack on the Hoopa. A large explosion was made and Hoopa got destroyed.
The end.
Credit scenes show Marshadow riding on baby Arceus through a field while sucking on a lollipop. The baby Arceus decided to create a lollipop on its own because it wanted one too. They both live happily ever after.
In hindsight, I can guess this was largely inspired by the Hoopa movie, the Marshadow movie, Terminal Montage's Legendary Battle Royale video, and the Gen 7 Anything Goes metagame being thrown into this one fictional match.