
Like I said, Substitute is to help take advantage of stuff like Ferrothorn and Clefable, either by setting one up as they switch out or by blocking any greedy Knock Offs/Thunder Waves. Another great thing about Substitute is that because of Heatran's typing, it can avoid taking damage from behind a Substitute easily, only being threatened by Infiltrator Dragapult and Surging Strikes Urshifu; this gives it free turns against many mons that it would usually have rough matchups against such as Garchomp, Tyranitar, Glowking, and various Water-types while solidifying its already solid matchups. Magma + Taunt is the usual "fuck whatever is coming in" combo that annoys many bulkier foes, and with the aforementioned Substitute, it gives Heatran more opportunities to use these moves more safely, such as needing to land Magma Storm after a miss or being able to Taunt against a slower mon without worrying about taking damage. Earth Power covers opposing Heatran, Waters, etc. Flash Fire gives Heatran extra opportunities to set up Substitute thanks to the Fire immunity and powering up Magma Storm never hurts.

I needed a way to deal with Surging Strikes Urshifu as well as something that could lure in stuff like Shed Shell Toxapex and Assault Glowking and Knock Off their items; luring in Ferrothorn for Heatran to take advantage of is another bonus. Azumarill was what I settled on; thanks to its typing and invested bulk it could check Urshifu decently well and it invites in all the aforementioned mons for Heatran's benefit. I originally ran Choice Band but its lack of bulk was noticeable, and then breaking power still wasn't very encouraging, not to mention the move locks could be rather exploitable, so I swapped over to an Assault Vest set for the extra special bulk and ability to swap moves. Max HP investment lets always live 2 CB Surging Strikes from full as well as let it swap into Dragapult semi-reliably if needed, the Speed is for... honestly I forget (checks Speed tier list)... uninvested Tyranitar, sure; rest goes into Attack to hit as hard as possible. This could have been a Knock Off Tapu Fini instead, but I preferred the physically-oriented nature of Azumarill more, as it let it check Volcarona pretty reliably thanks to Assault Vest and Aqua Jet. Aqua Jet also helps pick off Blaziken in a pinch.

Wanted hazard removal, a way to punish Knock Off and other contact moves, a check to Rillaboom/Kartana/Torn-T/Water-types, and a Ground-immunity, all with an offensive kick to it. Hey what do you know, Zapdos can provide all that. It's not the best Defogger in the world, but with the team's offensive lean, I didn't mind it too too much. Max HP investment lets it check stuff more reliably thanks to the extra bulk, and I EV'd it to outspeed +Speed base 70s (Timid Volcanion and everything below that) because it felt like a decent benchmark, put the rest into SpAtk with a Modest nature to let Zapdos bring on the pain. Static paralysis is also useful for giving Heatran extra opportunities to set up a Substitute safely.

Mandatory Ground-type, but I didn't want to let up on the team's offensive pressure, so SD Garchomp was my choice. Does all the shit you expect SD Chomp to do; Fire Fang was my preferred coverage move to hit annoying stuff like Buzzwole, Corviknight, and Ferrothorn, but Aqua Tail could be run instead if hitting Lando-T + Balloon Heatran is preferred.

With Heatran running a rather offensive set with little utility, I wanted a second Steel-type that could cover stuff like Weavile, Tapu Lele, the Grass-types, etc. Ferrothorn was a no-brainer choice, it offered all that I wanted defensively and could bring extra utility with Stealth Rock, Knock Off, Thunder Wave, and Iron Barbs contact punishment. Like Zapdos, it can swap into Surging Strikes if Urshifu tries to scare out Heatran behind a Substitute and punish it with Iron Barbs, or reveal that it is Protective Pads, making it easier to handle damage-wise. Power Whip is the fourth move in order to directly threaten bulky Waters and Grounds that may give the team, and especially Heatran, trouble. EV'd to avoid the 2HKO from Modest Specs Dragapult Shadow Ball with rocks up.

I needed a check to threats like boosted Garchomp and a way to swap into Shadow Ball more reliably than "it barely avoids the 2HKO", so Weavile was a natural last pick for me. Went with the Boots SD set so that hazards wouldn't dig into Weavile, letting it swap in more reliably, and it gave me an extra setup wincon. Like Azumarill, it can lure in mons like Toxapex and Tapu Fini that could annoy Heatran and removes their items with Knock Off. icicle Crash was the Ice move of choice cuz I figured the flinch chance paired well with paralysis support as well as not being contact, but honestly Triple Axel is better even with the accuracy and contact issues. Being the fastest unboosted mon on the team is also very nice, as it gives the team more room to play around stuff like Torn-T and non-Scarf Blacephalon.