Azumarill @ Sitrus Berry
Ability: Huge Power
EVs: 92 HP / 252 Atk / 164 Spe
Adamant Nature
- 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.