Azumarill @ Sitrus Berry
Ability: Huge Power
EVs: 92 HP / 252 Atk / 164 Spe
- Belly Drum
- Aqua Jet
- Play Rough
- Knock Off
The team is weak to darkspam. Two members boost Bisharp's Attack, while Keldeo has no recovery, meaning that (for example) Weavile could pick Keldeo off after a boosted Bisharp weakens it. Also, Volcarona can get to +1 ez vs Tangrowth and Jirachi and if it has Giga Drain it can eliminate Keldeo. Moreover the team has no priority, no cleaner, no setup... BD Azumarill solves these problems. It's also a backup Fighting-type resist, since Lando-T is the king of getting pressured, and a needed Dragon immunity, since Scarfrachi has a nasty tendency to become setup fodder if it stays in for too long.
Keldeo will wear down Azumarill's checks (such as Lati@s), while Healing Wish support from Jirachi gives it another chance at sweeping. More generally, volt-turn support is great for Azumarill, getting it in on setup fodder and wearing things down into range of +6 Aqua Jet.
Latias's high Special bulk really helps you from having to sac a Pokemon each time Zard-Y or Specs Keldeo comes in. Psyshock allows you to beat SubCM Keldeo who can easily sub up in front of Jirachi and Lando-T while Thunderbolt allows you to dent Manaphy and Suicune who can boost up once Mega Manectric is gone.
This team has a very difficult time reliably dealing with Keldeo in spite of having Assault Vest Tangrowth because Keldeo is free to spam Fighting STAB vs the team, as Lando-T is the only Fighting resist on the team, which really sucks. With Latios, Keldeo will be clicking Scald/Icy Wind much more often, attempting to predict incoming Latios, allowing you more freedom when pivoting around with Tangrowth/Keldeo on your team, which is really nice. Additionally, while the team has a couple of checks to Zardy, it has absolutely nothing to pivot into if it gets in on a free double vs the other three members on the team, so Specs Latios adds another dimension to the team vs Zardy, being able to pivot in a couple times and fire off terrifyingly powerful Choice Specs boosted attacks, which makes Zardy more than manageable if you can play your rocks aggressively and keep them up throughout the match. Additionally, the team lacks any sort of breaking aside from Keldeo, which is a recipe for disaster, so Latios can bust through common defensive teams with its ability to Trick a Choice Specs onto defensive mons and cripple them, not to mention that it can just bust through shit with Specs-Boosted attacks. Realistically, you could run LO Roost Latios here, but this team doesn't really need Roost since Keld+Mane check Zardy and you have more than enough counterplay for opposing Keldeo.
The Mane/Lando group is a standard turn core which was really popular in XY. Both take neutral from rocks. The other pivots on the team are keldeo and Tangrowth, one of which doesn't mind hazards but Tangrowth relies on his pivoting to stay healthy. In other words, AV tangrowth's effective recovery is hurt disproportionately by hazards because he has no other way to gain back his main draw, bulk. Rachi's healing wish is nice, but it's going to be aimed at Mega Mane if at all possible.
It does help alleviate Bisharp's issue by outspeeding and stealing his stab resists while threatening burn. Mainly, this just allows keldeo to feel better about being foddered off since Starmie should always be able to handle bisharp on checks. This is also a decent counter-specs keldeo set, although you're still SOL vs anything sub/cm varianted. I feel like there are better picks since RT can be so underwhelming, but the fifth mon is trying to fill a unique set of issues (missing hazard clear, team empowers bisharp's sucker punch, missing keldeo counter) that aren't really easy to fill.
Heatran @ Air Balloon/Leftovers
Ability: Flash Fire
EVs: 48 HP / 208 SpA / 252 Spe
IVs: 0 Atk
- Magma Storm
- Earth Power
Forms a FWG core with Tang and Keldeo, gives the team a wow absorber and something to face Mega Sableye, and isn't scared by Thunder Wave Clefable like Jirachi, it also gives the team another necessary Fire Resistor alongside Keldeo. Helps against Special Defensive Talonflame with Wow, whom can potentially win the 1v1 against MManectric, and the rest of the team does not like coming in on Wow or the flying stab, adding to that Tangrowth and Jirachi also give Talonflame easy setup opportunities, lastly helps against Knock Off /Leech Seed Mega Venusaur whom can wear down Jirachi, the only reliable answer to said threat other than scald hax
The EV Spread allows it to function as a Keldeo switch in due to Dry skin + typing letting no moves except HP flying2HKO it while also checking common darkspam pokemon such as Weavile and Bisharp (even at +3 assuming you are at full HP with no hazards; +2 otherwise.). Swords dance allows it to both setup on Keldeo locked into water moves or walls and cleans up weakened teams that voltturn creates with Sucker Punch. Sucker Punch also provides an opportunity to revenge kill offensive psychic types like Lati@s, Mega-Ala, Starmie, and Mega-Medicham (if weakened) who would otherwise place a lot of pressure on Jirachi to check/revenge kill. Belly Drum Azu would also otherwise sweep this team but this checks it assuming Gunk Shot doesn't miss.