Theorymon time! Yay!
Item: Toxic Orb
Ability: Poison Heal
Evs: 252hp/252atk/4def or spdef with adamant nature
-Facade
-Knock Off
-Drain Punch
-Substitute/ThunderWave/Toxic
This is just a bulky regi set like any other, he can take some hits and hit hard in return, cant hit extremely hard like deoxys a and rayquaza, but he serves as a nice bulky attacker and he can also support by slowing down the opponent with thunderwave or dealing residual damage with toxic.
252+ Atk Protean Deoxys-A Extreme Speed vs. 252 HP / 0 Def Regigigas: 169-201 (39.8 - 47.4%) -- 93.5% chance to 3HKO after Poison Heal
252+ Atk Life Orb Aerilate Rayquaza Extreme Speed vs. 252 HP / 0 Def Regigigas: 250-294 (58.9 - 69.3%) -- guaranteed 2HKO after Poison Heal
252+ Atk Regigigas Facade (140 BP) vs. 252 HP / 0 Def Rayquaza: 321-378 (77.5 - 91.3%) -- guaranteed OHKO after Stealth Rock
252+ Atk Regigigas Facade (140 BP) vs. 252 HP / 0 Def Arceus: 252-297 (56.7 - 66.8%) -- guaranteed 2HKO after Leftovers recovery
252+ Atk Adaptability Arceus Extreme Speed vs. 252 HP / 0 Def Regigigas: 168-198 (39.6 - 46.6%) -- 88.9% chance to 3HKO after Poison Heal
This basically means that it can work as
a check to the biggest extreme speed abusers in the tier. Id like to hear some feedback from this set as im not an expert at battling and even less at theorymoning.