Format: National Dex Anything Goes
Arceus-Dark @ Dread Plate
Ability: Multitype
EVs: 252 HP / 160 Sp.Def / 96 Spe
Timid Nature
- Judgment
- Recover
- Refresh
- Calm Mind
Unlike normal sets which have 160 Def, they are shifted to Sp.Def to allow Arceus Dark stall out Calyrex-S, Yveltal, etc. while 96 Spe makes along with Timid allows to outsped all 330> Pokemon. However, a more bulkier spread of 252 HP/ 252 Sp.Def/ 4 Spe can be chosen to take attacks from Yveltal and Calyrex-S far easier, but if that is done then support moves like Defog aren't recommended. Refresh allows it combat status better, but if you have Heal Bell support then go for other moves like Toxic/Defog (though Ho-Oh does that better). Will-o-Wisp can be interesting choice as it allows to burn Zacian-C on switch-in, shifting important momentum to your side.
Apart from Calm Mind stalling, there's not much Arceus-Dark can do. Yveltal and Tyranitar are doing the job better because: Yveltal has no weakness to Pollen Puff and gets Sucker Punch, Tyranitar is much more bulkier despite super effective moves, it can also provide Stealth Rock support and also Pursuit trapping.
Some important calculations:
+2 252 SpA Calyrex-Shadow Pollen Puff vs. 252 HP / 252+ SpD Arceus-Dark: 298-352 (67.1 - 79.2%) -- guaranteed 2HKO
Be prepared for people like me who use Baton Pass and Buginium Z.
+2 252 SpA Calyrex-Shadow Savage Spin-Out (175 BP) vs. 252 HP / 252+ SpD Arceus-Dark: 578-682 (130.1 - 153.6%) -- guaranteed OHKO
This can be quite tricky. Fairium Z isn't that used on Calyrex-S, so sadly Yveltal shines and Tyranitar too on this spot.
+2 252 SpA Calyrex-Shadow Savage Spin-Out (175 BP) vs. 252 HP / 252+ SpD Yveltal: 332-391 (72.8 - 85.7%) -- guaranteed 2HKO after Leftovers
That's it. While Tyranitar and yveltal do the job million times better, I guess we can use this :P