Okay now, I only have 3 pokemon, and they're not leaving, but suggest other three, Please?
Mixed Groudon@red orb
Ability: drought
Nature: quiet
EVs: 252 spa, 116 spd, 136 atk
- stone edge
- fire blast
- solar beam
- precipice blades
Coverage: 0 not very effective/no effect, 258 normal efficiency, 659 super effective
Damage calculations
252+ SpA Groudon-Primal Fire Blast vs. 252 HP / 0 SpD Arceus in Harsh Sunshine: 282-333 (63.5 - 75%) -- guaranteed 2HKO
252+ SpA Groudon-Primal Solar Beam vs. 252 HP / 0 SpD Arceus: 136-161 (30.6 - 36.2%) -- 55% chance to 3HKO
136 Atk Groudon-Primal Precipice Blades vs. 252 HP / 0 Def Arceus: 202-238 (45.4 - 53.6%) -- 38.7% chance to 2HKO
136 Atk Groudon-Primal Stone Edge vs. 252 HP / 0 Def Arceus: 112-132 (25.2 - 29.7%) -- guaranteed 4HKO
Note: Should Work-up pass into, little healing method (healing wish best chance)
Full Support Jirachi@Agauv Berry
Ability: serene grace
Nature:Bold
EVs: 252 Def, 200 SpD, 56 Hp
- doom desire
- toxic
- healing wish
- stealth rock
0 SpA Jirachi Doom Desire vs. 252 HP / 0 SpD Arceus: 129-153 (29 - 34.4%) -- 3.1% chance to 3HKO
Jirachi’s only purpose is to set up and heal Groudon. Setting up can help Groudon deal with more bulky/powerful threats.
Super Mew@Normalium Z
Ability: synchronize
Nature: quiet
EVs: 252 Atk, 252 SpA 4 SpD
- baton pass
- work up
- amnesia
- transform
252+ SpA Mew Psychic vs. 252 HP / 0 SpD Arceus: 115-136 (25.9 - 30.6%) -- guaranteed 4HKO
Mew has 3 uses, work-amnesia pass onto Groudon, taking out weaker threats, and z-transform to copy and heal onto a good Pokemon.
I did calculations on a Zero Def investment Arceus.
Source: https://pokemonshowdown.com/damagecalc/index.html