Your team is a nice HO Styled thingy which looks weak to:
Rayquaza-Mega: Seriously give me a thing that counters it and I'll give you my whole property. HO is weak af to it, and you know that it's good. Late-game, when Marsh and your Mega Ray would be weakened / picked off, you won't even be able to revenge kill the opposing Ray, and the Don is a hot SU Fodder for it. After a DD, it seriously picks up everything. Therefore, yer need something that can eat a +1 Dragon Ascent and OHKO it in return.
Necrozma-Ultra: Marsh's Sneak does 59%, and then it's a good looking sweep. Indeed, you have two revenge-r's in the team, but lo and behold, Maths exists. Let's say Marsh is in to revenge it. This'd mean, that you got it on a free switch, usually through pivoting from a slower Pokémon, or sacking your Pokémon and then brining another. Correct me if I'm wrong, because I didn't see no U-Turn / Volt Switch in your team, and so the second option applies. Then boom, you sack something and then bring Marsh / Mega Ray to revenge, which is not hot (No I don't reccomend Marsh or the Mega Ray on a manual switch no).
Random CM Ceus formes: Marsh exists, but those (CM Ceus) aren't supposed to complete a sweep once, and so when they switch into smth that counters Marsh (plenty options there), they all good . DarkCeus is used a lot out of of all CM Ceus, and after a +3 or smth, Judgement KO's or 2KO's half the thingies here. And, after Marsh boom boom'd, a sweep would look even tastier.
Xerneas: Xern can potentially sweep you ngl. Don has a nice chance to get OHKO'd with a +2 Focus Blast, which is bad. Scarf Xern even bad, if you don't know it's Scarf, you try to go for Ascent from Ray, but no Xern outspeeds and boom ggswp. Literally a big problem here.
Now, you'd have an urge to stop these things. Therefore, let's plunge into a very boring answer!!!
(I'm gonna list the Ceus formes that counter / check the above things btw)
Arceus-Fairy is a staple within the Anything Goes metagame thanks to its great offensive and defensive typing, expansive movepool, and impressive natural bulk. Due to this, it can reliably take on many potent threats within the metagame, such as Mega Rayquaza, Marshadow, Mega Sableye, Yveltal, and Zygarde-C.
See the analysis itself says that it's staple lols. Anyways, I usually hate sacrificing (that the spelling, duh?) a WHOLE teamslot on a HO Team for a Defogger, but I guess here it's necessary. It also gonna support you through ample of support moves, like Toxic, Wisp, and uh more.
I'm team-building and I need defensive speedy Arceus. Which form should I use? Give applicable reasons please.
Speedy? See, you can run Max Speed, but I don't recommend that on SupportCeus formes (exceptions exist like I exist). I usually do 16 Spe, as it then outspeeds neutral base-90's and everything below, like Primal's, etc. It won't be outright speedy, but that'll help as it increases bulk. Applicable reasons? Umm, it's a soft check to +1 Mega Ray's, counter to LO Marsh (can't come in on a +1 SSSSS, tho), counter to Gira, Xyg and uh a lot else.
Use Arceus-Fairy's defensive typing strategically by switching into Pokemon whose attacks it resists and capitalizing on opportunities to spread status and set or remove entry hazards.
Defog support is great ofc, and it'll help ye a lot. I highly recommend using it.
Arceus-Fairy @ Pixie Plate
EVs: 248 HP / 244 Def / 16 Spe
Judgment is Arceus-Fairy's strongest STAB move, allowing it to OHKO Marshadow, Yveltal, and Mega Rayquaza after Stealth Rock damage while doing substantial damage to Zygarde-C and Giratina. Recover ensures Arceus-Fairy can preserve its health throughout the match to let it switch into attacks such as Yveltal's Oblivion Wing repeatedly. Stealth Rock is a great option, as Arceus-Fairy is able to force out Mega Sableye and Yveltal, the latter of which may be equipped with Defog. Defog can be slotted onto Arceus-Fairy if entry hazard removal is hard to fit; however, its weakness to common trappers and hazard setters makes Defog a subpar option. Toxic allows Arceus-Fairy to deal with a few common switch-ins in Ho-Oh and Primal Groudon, ensuring these Pokemon cannot come in freely. Will-O-Wisp provides Arceus-Fairy with a way to impair Necrozma-DM and other Steel-types but is usually less useful than Toxic, as Necrozma-DM still threatens Arceus-Fairy, and other Steel-types can shrug off the burn damage with Leftovers and Leech Seed.
Arceus-Dark is one of the best Arceus formes in Anything Goes due to its great pure Dark typing. This grants it an immunity to Psychic-type attacks from Ultra Necrozma and Deoxys-A and Dark-type STAB Judgment to also effectively check common threats such as Necrozma-DM, Ultra Necrozma, and Mega Gengar. Arceus-Dark also beats Shadow Tag users like Mega Gengar and Gothitelle, which makes it an excellent support Arceus forme on balance teams.
Hmm do I have to say more (yes). DarkCeus does nicely on your team as it helps a lot against Ultra Necro's, which is like OH. PsySpam with Deo-A is :O, and a check to that is sweet. Watch out for the damn Superpower tho, and try scouting to smth that can eat a Superpower and stall out the turns of PsyTerrain.
It's offensive capabilities are also wow, as I mentioned before, it can rip through teams after a CM Boost.
Arceus-Dark @ Dread Plate
EVs: 252 HP / 4 Def / 252 Spe
- Calm Mind
Calm Mind allows Arceus-Dark to pressure the opposing team offensively. Judgment is Arceus-Dark's STAB move, having no immunities and helping it to threaten Mega Gengar, Necrozma-DM, Ultra Necrozma, and Giratina. Recover is a necessary move, as it ensures longevity. Refresh removes status conditions such as Toxic poison and paralysis, allowing Arceus-Dark to set up on most Arceus formes lacking Perish Song or Roar and other specially defensive walls that rely on wearing it down with Toxic.
If you want a support set, use this one:
Arceus-Dark @ Dread Plate
EVs: 252 HP / 160 Def / 96 Spe
Judgment has solid neutral STAB coverage and hits Ultra Necrozma, Necrozma-DM, Arceus-Ghost, and Mega Gengar for super effective damage, preventing them from setting up. Recover restores Arceus-Dark's HP, allowing it to check the Pokemon it is supposed to check. Will-O-Wisp is the main status move used on Arceus-Dark, as it reduces the target's Attack, letting Arceus-Dark check physical attackers more easily. Toxic can be used over Will-O-Wisp to punish switch-ins like Primal Groudon and Arceus-Fairy. Defog is used to clear off entry hazards.
Arceus-Poison is a premier counter to Fairy-types that can provide fantastic team support by setting or removing entry hazards. While Necrozma-DM and Magearna have their own advantages as Fairy-type counters, Arceus-Poison is unique in that it provides hazard support, has reliable recovery, and has the additional benefit of being able to check both Marshadow and Yveltal. Furthermore, access to Will-O-Wisp ensures that Arceus-Poison will not be setup bait for physical attackers.
Arceus-Poison @ Poisonium Z
EVs: 248 HP / 8 Atk / 8 Def / 148 SpD / 96 Spe
- Poison Jab
- Stealth Rock / Earth Power / Defog
Poison Jab is Arceus-Poison's primary attack of choice that can hit Fairy-types hard and has the added benefit of a poison chance to cripple switch-ins. Will-O-Wisp neuters opposing physical attackers, especially Mega Rayquaza and Necrozma-DM, preventing Arceus-Poison from becoming setup bait. Stealth Rock is generally the best support move of choice, as it can be set on many common Defoggers in the metagame such as Arceus-Fairy and Arceus-Water. Defog can be used if the team requires a Defogger but is usually inferior due to the fact that Arceus-Poison is countered by Primal Groudon, the most common Stealth Rock setter in the metagame. If neither Stealth Rock nor Defog is necessary, Earth Power can be used to 2HKO Mega Gengar even with a Special Attack-lowering nature and hit Primal Groudon for more damage.
Also, you can run Psych Up on the last slot, as it'd better it's MU against Xern and other SU Sweepers, but that's conditional and only run that if you got a relevant Defogger / Rocker.
There we are. Fairy, Dark and Poison Ceus. Fairy checks Mega Ray and CM DarkCeus (don't let it setup quickly...), Dark checks U-Necro, and Poison checks Xern.
Very sorry for such a boring answer oof lol.
P-Ogre: Looks.. Ok I guess I get the point, you trap some Ceus formes, and faint them for some other teammate to pull a sweep, but nah ain't gonna work. You aren't running Rest, which means that it'd be down quickly ngl, and then boom Block becomes a waste of a moveslot. I'd say Rest > CM on it.
But I'd also say, don't run it. Go for DarkCeus instead. It repairs your MU against U-Necro, and can pull a sweep. Ogre was good, but DarkCeus maybe better here.
Don: No you don’t need speed on it. The set is Sassy with 252 HP / 56 Def / 220 SpD. This makes you a better wall overall, and aids you to set Rocks and all throughout the match.
Hope it helped!