Cresselia - is your defensive setter, but it's also fat enough to live a Gengar's Shadow Ball. Lum Berry is for setting up on Breloom and T. Wave Togekiss, which is generally a large pain in the ass for TR setters. Moonlight let's it sit on Dragons all day (especially Garchomp) and Ice Beam hits them hard even without investment. Lunar Dance is for when you're ready to either heal a breaker and get them in for free after a TR. Yeah yeah!
Sp Def Gardevoir - lets it take a hit from +3 Manaphy and get in a breaker and like Cres, it also sets up freely on Latios. Trace is a very nice ability, letting it switch into Flash Cannon-less Heatran easily and makes it so Magma Storm can't trap it if it yoinks Flash Fire and you aren't ready to Teleport or Healing Wish. Trace also "no u"s back various Intimidaters like Salamence and Arcanine, which is cool. Teleport lets you slow pivot out to get in a breaker if you want to maintain Garde for a bit and aren't wanting to heal up a breaker yet with Healing Wish. Garde takes advantage of Tangrowth and Slowbro, Teleporting out to the breakers while healing itself with Regenerator. STAB Moonblast let's it hit the Dragons and Breloom.
Crawdaunt - is your first breaker. Come on, it's TR. Nothing can hard switch in, even Tangrowth after an SD. Don't be afraid to Knock Off opposing Azurmarrils to deny them Belly Drum or its Band. Breloom even dies to a Knock Off + Aqua Jet in TR. It will make Cresselia's life easier.
Band Azurmarill - is your second breaker. Having two water breakers together, both of whom brutalize Water types and Dragons is an INSANE amount of offensive pressure (especially when you factor in your healing moves to bring these guys back to full). STABs and priority are a given, but Superpower hits Empoleon on the switch in, while also easing prediction when staring down a water weak mon like Tyranitar/Heatran but also has a water resist/immunity sitting behind it waiting to switch in, like Gastrodon or Manaphy.
Nidoking - Besides having an electric immunity and picking up Toxic Spikes, this guy brutalizes Stall and Offense alike with its strong STABS, coverage and priority. Against Stall it switches in on Clefable and goes to town. No min speed here, so it can outspeed Stall without needed to set up TR, but it's also still slow enough that it WILL do work against Offense and Balance in TR. Poison Jab hits Blissey on switchin expecting a full special set. Ice Beam hits Gliscor and the Dragons and Tangrowth hard, as well as being a strong option for Skarmory. Earth Power is your best option against Scizor and hits other Steels. (Flamethrower could also work over Ice Beam, but I think IB is generally better.) Sucker Punch lets it hit Offense mons like Gengar outside TR.
These are the Pokémon you will receive!
Nonshiny Mew @ Mental Herb
Ability: Synchronize
EVs: 252 HP / 244 Atk / 12 SpA
Quiet Nature
IVs: 0 Spe
- Overheat
- Stealth Rock
- Trick Room
- Explosion
Gardevoir (M) @ Lum Berry
Ability: Trace
EVs: 252 HP / 56 SpA / 200 SpD
Sassy Nature
IVs: 0 Spe
- Psychic
- Teleport
- Healing Wish
- Trick Room
Azumarill (M) @ Choice Band
Ability: Huge Power
EVs: 252 HP / 252 Atk / 4 SpD
Brave Nature
IVs: 0 Spe
- Waterfall
- Play Rough
- Aqua Jet
- Superpower
Crawdaunt (M) @ Life Orb
Ability: Adaptability
EVs: 252 HP / 252 Atk / 4 SpD
Brave Nature
IVs: 0 Spe
- Waterfall
- Knock Off
- Aqua Jet
- Swords Dance
Nidoking (M) @ Life Orb
Ability: Sheer Force
EVs: 4 HP / 252 Atk / 252 SpA
Brave Nature
- Earth Power
- Poison Jab
- Ice Beam
- Sucker Punch
Cresselia (F) @ Lum Berry
Ability: Levitate
EVs: 252 HP / 252 Def / 4 SpD
Relaxed Nature
IVs: 0 Spe
- Ice Beam
- Moonlight
- Trick Room
- Lunar Dance
I did not create this team but found it on Smogon, I would highly recommend checking out smogon for team ideas.