Well, what do we got here?
A Pokemon Mystery Dungeon fanfic?
Where'd that come from?
In all seriousness, I've had this one sitting around forever.
Finally got back to it, so here, have the prologue.
Submitted from mobile, hence the weird method for posting.

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The Legendary Pokemon were arguing. Again. Hoopa was being scolded for stealing one of Arceus’ Life Plates.
“All right, just return the Plate and we can forget this whole thing ever happened.” Arceus glared down at Hoopa.
“No no no! It's mine now! I stole it fair and square!” Hoopa yelled back.
“Hoopa, if you won't return the Plate willingly, I'll have to take it back by force. You wouldn't like that.” While Arceus’ tone was calm, everyone present knew that the Alpha Pokemon was getting VERY annoyed with Hoopa.
“Grrrrrrr… Fine! Have your stupid Plate back!” Hoopa pulled out the Plate and threw it on the ground. Arceus retrieved his Plate.
Meanwhile, some of the Legendaries were arguing over whether Genesect and Mewtwo even counted as true Legendaries.
“Insanely powerful? Check. Unique in the world? Check.” Mew defended his/her genetic descendant.
“You're only defending them because Mewtwo is related to you!” Moltres snapped.
“That’s not it at all!” Mew denied.
“Why don't we get Reshiram, the embodiment of Truth, and have HER settle this argument?” Moltres challenged.
“Why didn't we do that earlier? Would've save us a lot of arguing.”
Reshiram was brought in. She looked at the two. Then she noted, “Being a Legendary is a somewhat arbitrary label. You ever see the two from Alola? They Evolve, yet they're still considered Legendaries. Being artificial has far fewer implications than Evolving from another Pokemon.”
Moltres muttered, “Blast! She's right!”
Then Arceus called out to the Legendaries. “Ahem. I have some announcements to make. First off, it has been voted that the troublemakers among us are going to be executed. That includes Thundorus, Tornadus, Hoopa, Giratina, Groudon, and Kyogre. Will they please come up front?”
Arceus looked around. The Legendaries he had named had seemingly vanished into thin air.
He mumbled “Well, it was worth a shot.”
A voice called “OBJECTION! When did we vote for this?”
Arceus looked at the Legendaries. “It was last week.”
“And who exactly voted?”
Dialga, Palkia, Ho-Oh, Moltres, Articuno, Zapdos, Rayquaza, Yveltal, Kyurem, and Landorus. Oh, and I voted.”
“I assume you voted for the death penalty.”
Arceus was visibly miffed. “No, I didn't. Troublemakers or not, they're vital to how the world functions. I told you that this is why I didn't want to share the decision-making process.”
The entire Hall of Origin went mad with chattering, squabbling Legendaries. Arceus just groaned, his immortal patience thoroughly tested.