Mega Venusaur is a key part of the defensive core, having an incredibly powerful defensive typing after considering Thick Fat, only weak to Psychic and Flying while resisting multiple types and being neutral against Ground. Sludge Bomb lets Mega Venusaur attack the threats that it can switch into like Tapu Koko, and allows it to poison walls like Porygon2 and Mega Sableye. Giga Drain gives Mega Venusaur recovery and lets it hit Ground-type Pokemon that could otherwise threaten the team, as well as Water-type Pokemon it can switch into. Leech Seed helps it beat defensive Pokemon like Chansey, removing their health while giving Mega Venusaur additional recovery. Synthesis is reliable recovery that lets Mega Venusaur stay healthy throughout the battle. Chlorophyll will rarely matter, but can be useful on occasion such as when revenge killing a weakened Mega Charizard Y. Defensive investment helps it answer physical threats better, with 16 Speed EVs to outspeed Adamant Azumarill.

Toxapex is an incredible defensive pivot due to Regenerator, allowing it to switch in and out of Pokemon without using Recover. Scald allows Toxapex to pressure opposing Pokemon and threaten them with a burn. Haze prevents Pokemon from setting up on Toxapex, and allows Toxapex to remove boosts from Pokemon like Kommo-o and Volcarona. Toxic Spikes is a key element of the defensive strategy, wearing down opposing defensive Pokemon like Mega Sableye and setting opposing offensive Pokemon on timers. Recover alongside Black Sludge and Regenerator helps Toxapex stay healthy throughout the whole battle. Defense EVs helps it answer threats like Mega Pinsir, while its natural bulk and typing still lets it answer Pokemon like Mega Charizard Y and Volcarona without Special Defense investment.

Crobat is the third Pokemon of the defensive core, with a key immunity to Ground-type moves that prevent powerful wallbreakers like Choice Band Excadrill and Choice Band Diggersby from locking themselves into Earthquake. Additionally, it provides entry hazard removal and some pivoting for the team. Brave Bird helps it hit threats it outspeeds like Mega Gallade and Mega Pinsir hard even without Attack investment. U-Turn allows it to pivot out of Pokemon it cannot beat to bring in allies better suited against them, and helps bring Nidoking or Gengar in on switches. Defog lets Crobat remove hazards, while Roost alongside Black Sludge gives Crobat longevity. Infiltrator lets Crobat hit Pokemon behind Substitute and ignore Reflect and Light Screen. 192 Speed EVs with a Jolly nature lets Crobat outspeed Greninja and everything slower like Alakazam, with the rest in Defense for additional bulk.

Muk-Alola is the last Pokemon of the defensive core, functioning as the main answer to Psychic-type moves that threaten the rest of the team as well as powerful special attackers like Mega Charizard Y. Poison Jab and Knock Off are strong STAB moves from its 105 base Attack, and has added utility in a chance to poison (boosted by Poison Touch) and item removal. Pursuit lets Muk-Alola trap threatening Pokemon like Raichu-Alola. Fire Blast is coverage to hit Pokemon like Mega Scizor that the rest of its moves cannot hit well. Assault Vest and full Special Defense investment boosts its special bulk to monstrous levels so it can most effectively assist the rest of the team against special attackers. 12 Defense EVs lets Muk-Alola survive Choice Scarf Victini's V-Create always.

Nidoking doubles as both a special wallbreaker and an entry hazard setter. Earth Power is its main attacking option, hitting extremely hard, able to 2HKO even Pokemon like Mega Sableye (after Stealth Rock damage). Flamethrower and Ice Beam are coverage options. Earth Power with Flamethrower allows Nidoking to dismantle Steel teams after Heatran's Air Balloon is broken, while Ice Beam hits Flying- and Dragon-type Pokemon that Nidoking might otherwise struggle to hit. Stealth Rock allows Nidoking to assist the team by wearing down the opposing team whenever they switch. Life Orb boosts the power of all of Nidoking's attacking moves, with Sheer Force to strengthen them further and remove the Life Orb recoil.

Gengar is the speed control of the team, able to revenge kill, clean weakened teams, and occasionally act as a check to Pokemon like Choice Band Diggersby locked into a Normal- or Fighting-type move due to its Ghost typing. Sludge Wave and Shadow Ball are its main STAB moves. Sludge Wave hits hard and has a tiny chance to poison Pokemon like Mantine that might switch in. Shadow Ball hits Psychic-type Pokemon super effectively, helping the Psychic matchup immensely, and can often be more spammable than Sludge Wave as only few teams carry Ghost-type resists. Focus Blast is powerful coverage, able to beat Pokemon like Choice Scarf Excadrill. Trick lets Gengar cripple Pokemon like Gliscor and Chansey that might switch in on it. Choice Scarf allows Gengar to function as speed control and additionally enables Trick.