Lemme get a hand with this
Kyogre
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Kyogre @ Life Orb
Ability: Drizzle
Hidden Power: Flying
EVs: 4 Def / 252 SpA / 252 Spe
Modest Nature
IVs: 0 Atk
- Origin Pulse
- Ice Beam
- Calm Mind
- Hidden Power [Flying]
There's no single reason to use Kyogre without the Dynamax breaker set. LO + 4MSS is absolutely terrible, Calm Mind with Hidden Power [Flying] is much more potent as a Dynamaxer and wallbreaker.
With Calm Mind, Kyogre is able to break through bulky checks such as Chansey, Blissey, and Primal Groudon which it can't break normally with a Scarf set or as in Primal forme. Ice Beam as Max Hailstorm OHKOes Mega-Rayquaza, while Origin Pulse has the power to OHKO or 2HKO almost every neutral match-up, Hidden Power Flying as Max Airstream boosts your Speed, thereby making it faster so that faster threats like Calyrex-Shadow, Mega-Ray, Zacian-C can no longer check it offensively. Life Orb is to boost your firepower.
Some calcs:
+1 252+ SpA Life Orb Kyogre Max Hailstorm vs. 252 HP / 206+ SpD Groudon-Primal: 272-320 (67.3 - 79.2%) -- guaranteed 2HKO
+1 252+ SpA Life Orb Kyogre Max Geyser vs. 4 HP / 252+ SpD Eviolite Chansey in Rain: 352-417 (54.8 - 64.9%) -- guaranteed 2HKO
Modest is chosen for more power. You can also choose Timid to outspeed Calyrex-Shadow and Sword Doggy at +1 Spe, but that's not always happening as compared to dealing damage to slower threats.
Mega-Rayquaza --> Arceus-Water
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Arceus-Water @ Splash Plate
Ability: Multitype
EVs: 252 HP / 132 Def / 124 Spe
Bold Nature
IVs: 0 Atk
- Judgment
- Recover
- Refresh
- Toxic
M-Ray and Sword Dog on same team seems to be more demerits. M-Ray become worse after DLC 2 came, as it gets easily revenge killed by Calyrex-S and Sword Dog all of whom are faster than it. Stealth Rocks weakness seems to be suffocating for it as well. Hence, to improve your MU against Primal Groudon as well as Kyogre, you had rather appreciated a better check to those. That's why we're having WaterCeus now in our team.
This set allows it to punish Primal Groudon through Toxic, while using its great bulk to Recover stall. Refresh makes it a good status absorber, one thing the team seems to be lacking. Judgement is STAB and generally the move choice to go, as it prevents it from getting walled by Necro Dusk Mane. 124 Spe EVs allow it to outsped Max Spe Base 90s, while the rest are invested in HP and Defense to get a better overall bulk.
Zacian-Crowned
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Zacian-Crowned @ Rusted Sword
Ability: Intrepid Sword
EVs: 4 HP / 252 Atk / 252 Spe
Adamant Nature
- Behemoth Blade
- Wild Charge
- Close Combat
- Assurance
The set's just a bit changed to have better performance. You really don't need Swords Dance as it's already hitting like a truck, but that's mainly for Necro Dusk Mane. Assurance deals double damage if target is chipped on the same turn via Rocks, etc. which means you can dispose off NDM easily as it gets KOed by a CC after Assurance with Rocks set-up. Behemoth Blade is pretty much all rounded and fine. Wild Charge is for WaterCeus and Ho-Oh friends, which wall the full set otherwise.
Necrozma-Dusk-Mane
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Fine set. You can always go with Toxic over Knock Off so as to wear down things like GroundCeus, Primal Groudon, DarkCeus, WaterCeus, etc. all of which wall Knock Off and your STAB move. Knock Off should only be really used for Ho-Oh's Boots, but as we already have Kyogre and WaterCeus you won't face much problems.
Yveltal
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Yveltal @ Heavy-Duty Boots
Ability: Dark Aura
EVs: 252 HP / 4 Def / 252 SpD
Careful Nature
IVs: 25 Spe
- U-turn
- Knock Off
- Defog
- Roost
As Ignis Aqua Herba already told, you can make this your main Defogger. Taunt doesn't seem to be much of use if you're not running any Speed, so I changed it to Defog. As an minor change, 25 Spe IVs makes you slower than opposing Yveltal so as to execute "Slow Turn" and to gain momentum by switch-ing out and moving last.
Calyrex-Shadow
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Calyrex-Shadow @ Ghostium Z
Ability: As One (Spectrier)
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Astral Barrage
- Substitute
- Baton Pass
- Nasty Plot
Ghostium the best!! Since you already have Kyogre that abuses Dynamax, something that isn't reliant on it is amazing. Ghostium gives a 195 BP nuke that is able to OHKO many leads, so it's great. You don't really need Psyshock for Chansey since you can hide behind Substitute and it can't Toxic you. It also improofs you from Ditto, so that's always a choice.
Final team with changes
Hope this helps!