Hey pplz I know that A LOT of us have a hard time shattering all of Arceus' Plates, as well as trying to catch it. I have a mini guide/tips/hints that will help you shatter all of Arceus' Plates in 7 turns or less. Catching it is a different story, I can only help you make sure that that you have as many poke/great/ultra are any other ball to catch it in.
Shattering The Plates Easily:
Idk if you guys know this but the Hold Item Choice Band is the perfect item to help shatter Arceus' Plates. However, this is only true if you have one or more pokemon that know any of the following moves: Earthquake, Blizzard, Muddy Water, Surf, or any other move(s) that can hit multiple targets.
Earthquake and Blizzard are bold because I STRONGLY SUGGEST that you give Choice Band to a pokemon that know either of these moves. Only just their super effectiveness against the plates is roughly 10 out of the 17. So if you have a pokemon that one of these 2 moves you and give it Choice Band, the plates that are super effectively hit will shatter in 2 or 3 turns (or less if it is a critical hit). BTW if you're gonna use blizzard, make sure you got elixier (or max) or eteher(or max)
Here is a list of the plates that Earthquake is super effective against:
Toxic Plate
Rock Plate
Flame Plate
Zap Plate
Iron Plate
Now for Blizzard:
Sky Plate
Toxic Plate
Insect Plate
Meadow Plate
Draco Plate
The the rest of the plates are normal effective with only 3 or 4 not very effective (save for the Sky Plate since Earthquake doesn't affect it and I forget the one for Blizzard). These plates will shatter in 2-4 turns (4 turns [maybe]= for not very effective. 2-3= normal effective.). These do not include critical hits.
The hard part about this is after the barrier around Arceus Shatters, get Arceus to the red zone and keeping your pokemon that knows Blizzard or Earthquake, and your team alive.
Capturing Arceus:
Okay before you even THINK about going to Raptor Shrine with a couple of Ultra Balls saying "this should be good enough." Okay how should I put this......Oh I know! How about NOT!!!!!! Before you go to Raptor Shrine, use the money you won from beating the Gaia Wings, which was somewhere between $10,000 and $12,000 each. What you should do is buy 10 pokeball 9 times, that way you get 9 premier balls as well as 90 pokeballs, and yes, I mean that you buy pokeballs 9 different times because not only do you get 99 balls for about 18,000, you still have about $40,000 or more. The next things you should buy are Timer Balls, because if you think about it each turn that passes increases capture success rate, and if you're like me, you be facing Arceus for a while. Its up to you, buy as many Timer Balls as you want. And finally Ultra Balls x20 which is $24,000. Now I would just like to say that I hope the people who are saying "but prof. oak gave me a master ball, I don't need to buy all of these." To which I hope that everyone knows that the master ball won't work, it would be to easy to catch then. As well as it was kinda obvious that the master ball wouldn't work against it.
Anywayz, this is the guide that hopefully get you guys an Arceus. Oh, one more thing, If you're saying to yourself "This guy's nuts, you can't catch Arceus in a pokeball, its impossible" and again...no you're wrong I caught Arceus with a pokeball besides, it'll take almost all your pokeballs to catch it, and they're only there if you run out of everything else.
EDIT: If you go to your house and sleep in your bed you will the the person that had Dialga and Palkia at Cave of Destiny