After completing your mission againstTeam Galactic atStark Mountain, you can challenge theBattleground where the Sinnoh Gym leaders and your formerMulti Battle partners can be fought against. They are randomly selected each day and can only be fought once a day. Every one of them only uses 5 Pokémon and all of them except Candice and Mira have at least one non-regional Pokémon.

Gym Leaders

For the Gym Leaders they have higher level teams than what they had before. Pretty much just about the same strategies will work here but just remember some of these Pokémon have moves that can counter their weaknesses.

Roark

Leader Roark Battleground Platinum Reward: $7800

Types: Rock Flying Ability: Rock Head Held item: None Aerodactyl♂Lv.62 Stone Edge Rock Physical   --       Aerial Ace Flying Physical   --       Earthquake Ground Physical   --       Dragon Claw Dragon Physical   --       Types: Rock Steel Ability: Sturdy Held item: None Probopass♂Lv.61 Earth Power Ground Special   --       Stealth Rock Rock Status   --       Discharge Electric Special   --       Stone Edge Rock Physical   --       Type: Rock Unknown Ability: Mold Breaker Held item: None Rampardos♂Lv.63 Head Smash Rock Physical   --       Zen Headbutt Psychic Physical   --       Avalanche Ice Physical   --       Earthquake Ground Physical   --       Types: Rock Ground Ability: Rock Head Held item: None Golem♂Lv.61 Stone Edge Rock Physical   --       Earthquake Ground Physical   --       Brick Break Fighting Physical   --       Flamethrower Fire Special   --       Types: Rock Dark Ability: Sand Stream Held item: Sitrus Berry Tyranitar♂Lv.65 Stone Edge Rock Physical   --       Crunch Dark Physical   --       Aerial Ace Flying Physical   --       Fire Fang Fire Physical   --

Gardenia

Leader Gardenia Battleground Platinum Reward: $7800

Types: Grass Flying Ability: Chlorophyll Held item: None Jumpluff♀Lv.61 Silver Wind Bug Special   --       Toxic Poison Status   --       Sunny Day Fire Status   --       Bounce Flying Physical   --       Type: Grass Unknown Ability: Flower Gift Held item: None Cherrim♀Lv.62 SolarBeam Grass Special   --       Leech Seed Grass Status   --       Toxic Poison Status   --       Sunny Day Fire Status   --       Type: Grass Unknown Ability: Chlorophyll Held item: None Bellossom♀Lv.61 Drain Punch Fighting Physical   --       Giga Drain Grass Special   --       Ingrain Grass Status   --       Sunny Day Fire Status   --       Types: Grass Ground Ability: Overgrow Held item: None Torterra♂Lv.63 Wood Hammer Grass Physical   --       Crunch Dark Physical   --       Earthquake Ground Physical   --       Stone Edge Rock Physical   --       Types: Grass Poison Ability: Natural Cure Held item: Sitrus Berry Roserade♀Lv.65 Leaf Storm Grass Special   --       Sludge Bomb Poison Special   --       Shadow Ball Ghost Special   --       Hyper Beam Normal Special   --

Fantina

Leader Fantina Battleground Platinum Reward: $7800

Type: Ghost Unknown Ability: Insomnia Held item: None Banette♀Lv.61 Shadow Claw Ghost Physical   --       Faint Attack Dark Physical   --       Thunderbolt Electric Special   --       Will-O-Wisp Fire Status   --       Type: Ghost Unknown Ability: Levitate Held item: None Mismagius♀Lv.63 Shadow Ball Ghost Special   --       Psychic Psychic Special   --       Magical Leaf Grass Special   --       Thunderbolt Electric Special   --       Types: Ghost Flying Ability: Aftermath Held item: None Drifblim♀Lv.61 Ominous Wind Ghost Special   --       Psychic Psychic Special   --       Silver Wind Bug Special   --       Baton Pass Normal Status   --       Type: Ghost Unknown Ability: Pressure Held item: None Dusknoir♀Lv.62 Rock Slide Rock Physical   --       Shadow Punch Ghost Physical   --       Double Team Normal Status   --       Protect Normal Status   --       Types: Ghost Poison Ability: Levitate Held item: Sitrus Berry Gengar♀Lv.65 Shadow Ball Ghost Special   --       Psychic Psychic Special   --       Focus Blast Fighting Special   --       Thunder Electric Special   --

Maylene

Leader Maylene Battleground Platinum Reward: $7920

Type: Fighting Unknown Ability: Intimidate Held item: None Hitmontop♂Lv.62 Triple Kick Fighting Physical   --       Aerial Ace Flying Physical   --       Quick Attack Normal Physical   --       Fake Out Normal Physical   --       Types: Grass Fighting Ability: Effect Spore Held item: None Breloom♀Lv.62 Stone Edge Rock Physical   --       Spore Grass Status   --       Mach Punch Fighting Physical   --       Seed Bomb Grass Physical   --       Types: Fighting Psychic Ability: Pure Power Held item: None Medicham♀Lv.63 Fire Punch Fire Physical   --       Ice Punch Ice Physical   --       ThunderPunch Electric Physical   --       Hi Jump Kick Fighting Physical   --       Type: Fighting Unknown Ability: Guts Held item: None Machamp♂Lv.64 Cross Chop Fighting Physical   --       Rock Climb Normal Physical   --       Earthquake Ground Physical   --       Stone Edge Rock Physical   --       Types: Fighting Steel Ability: Steadfast Held item: None Lucario♂Lv.66 Drain Punch Fighting Physical   --       Close Combat Fighting Physical   --       ExtremeSpeed Normal Physical   --       Bone Rush Ground Physical   --

Crasher Wake

Leader Wake Battleground Platinum Reward: $7800

Types: Water Dark Ability: Rough Skin Held item: None Sharpedo♂Lv.61 Aqua Jet Water Physical   --       Night Slash Dark Physical   --       Endure Normal Status   --       Slash Normal Physical   --       Types: Water Ground Ability: Damp Held item: None Quagsire♂Lv.61 Earthquake Ground Physical   --       Stone Edge Rock Physical   --       Yawn Normal Status   --       Surf Water Special   --       Type: Water Unknown Ability: Swift Swim Held item: None Floatzel♂Lv.63 Brine Water Special   --       Ice Fang Ice Physical   --       Crunch Dark Physical   --       Aqua Jet Water Physical   --       Types: Water Flying Ability: Intimidate Held item: None Gyarados♂Lv.62 Aqua Tail Water Physical   --       Avalanche Ice Physical   --       Bite Dark Physical   --       Giga Impact Normal Physical   --       Types: Water Grass Ability: Swift Swim Held item: Sitrus Berry Ludicolo♂Lv.65 Surf Water Special   --       Ice Beam Ice Special   --       Energy Ball Grass Special   --       Focus Blast Fighting Special   --

Byron

Leader Byron Battleground Platinum Reward: $7800

Types: Steel Flying Ability: Keen Eye Held item: None Skarmory♂Lv.61 Night Slash Dark Physical   --       Drill Peck Flying Physical   --       Rock Tomb Rock Physical   --       Stealth Rock Rock Status   --       Types: Electric Steel Ability: Magnet Pull Held item: None MagnezoneLv.62 Flash Cannon Steel Special   --       Thunderbolt Electric Special   --       Supersonic Normal Status   --       Thunder Wave Electric Status   --       Types: Steel Ground Ability: Rock Head Held item: None Steelix♂Lv.61 Gyro Ball Steel Physical   --       Ice Fang Ice Physical   --       DragonBreath Dragon Special   --       Sandstorm Rock Status   --       Types: Rock Steel Ability: Sturdy Held item: None Bastiodon♂Lv.63 Metal Burst Steel Physical   --       AncientPower Rock Special   --       Iron Defense Steel Status   --       Rest Psychic Status   --       Types: Steel Rock Ability: Sturdy Held item: Sitrus Berry Aggron♂Lv.65 Stone Edge Rock Physical   --       Metal Burst Steel Physical   --       Earthquake Ground Physical   --       Avalanche Ice Physical   --

Candice

Leader Candice Battleground Platinum Reward: $7800

Types: Dark Ice Ability: Pressure Held item: None Weavile♀Lv.62 Avalanche Ice Physical   --       Faint Attack Dark Physical   --       Taunt Dark Status   --       Slash Normal Physical   --       Types: Ice Ground Ability: Oblivious Held item: None Mamoswine♀Lv.61 Earthquake Ground Physical   --       Avalanche Ice Physical   --       AncientPower Rock Special   --       Hail Ice Status   --       Types: Grass Ice Ability: Snow Warning Held item: None Abomasnow♀Lv.61 GrassWhistle Grass Status   --       Avalanche Ice Physical   --       Wood Hammer Grass Physical   --       Ingrain Grass Status   --       Types: Ice Ghost Ability: Snow Cloak Held item: None Froslass♀Lv.63 Confuse Ray Ghost Status   --       Blizzard Ice Special   --       Ominous Wind Ghost Special   --       Hail Ice Status   --       Type: Ice Unknown Ability: Snow Cloak Held item: Sitrus Berry Glaceon♂Lv.65 Mirror Coat Psychic Special   --       Blizzard Ice Special   --       Shadow Ball Ghost Special   --       Water Pulse Water Special   --

Volkner

Leader Volkner Battleground Platinum Reward: $7800

Type: Electric Unknown Ability: Volt Absorb Held item: None Jolteon♂Lv.61 Charge Beam Electric Special   --       Pin Missile Bug Physical   --       Double Kick Fighting Physical   --       Quick Attack Normal Physical   --       Type: Electric Unknown Ability: Static Held item: None Raichu♂Lv.61 Charge Beam Electric Special   --       Thunder Wave Electric Status   --       Light Screen Psychic Status   --       Brick Break Fighting Physical   --       Type: Electric Unknown Ability: Rivalry Held item: None Luxray♂Lv.62 Thunder Fang Electric Physical   --       Fire Fang Fire Physical   --       Crunch Dark Physical   --       Ice Fang Ice Physical   --       Types: Water Electric Ability: Volt Absorb Held item: None Lanturn♂Lv.63 Discharge Electric Special   --       Surf Water Special   --       Signal Beam Bug Special   --       Ice Beam Ice Special   --       Type: Electric Unknown Ability: Motor Drive Held item: Sitrus Berry Electivire♂Lv.65 ThunderPunch Electric Physical   --       Fire Punch Fire Physical   --       Giga Impact Normal Physical   --       Brick Break Fighting Physical   --

Tag Battle Partners

You can also face against the characters that you teamed up with at different locations throughout the game earlier. Since they do not follow a type specialty like the Gym Leaders, your team must be more diverse before you face any of them. Like the Gym Leaders some of their Pokémon also have moves that can counter their weaknesses. Notably they still have the Pokémon they used before that fought alongside you (though in Cheryl's and Mira's case, theirs have evolved).

Cheryl

Pokémon Trainer Cheryl Battleground Platinum Reward: $7800

Type: Psychic Unknown Ability: Shadow Tag Held item: None Wobbuffet♀Lv.61 Counter Fighting Physical   --       Mirror Coat Psychic Special   --       Safeguard Normal Status   --       Encore Normal Status   --       Type: Water Unknown Ability: Water Veil Held item: None Wailord♀Lv.63 Avalanche Ice Physical   --       Earthquake Ground Physical   --       Water Spout Water Special   --       Brine Water Special   --       Types: Ghost Flying Ability: Aftermath Held item: None Drifblim♀Lv.61 Protect Normal Status   --       Toxic Poison Status   --       Ominous Wind Ghost Special   --       Fly Flying Physical   --       Type: Fighting Unknown Ability: Thick Fat Held item: None Hariyama♂Lv.62 Stone Edge Rock Physical   --       Bullet Punch Steel Physical   --       Close Combat Fighting Physical   --       Earthquake Ground Physical   --       Type: Normal Unknown Ability: Natural Cure Held item: Sitrus Berry Blissey♀Lv.65 Counter Fighting Physical   --       Softboiled Normal Status   --       Psychic Psychic Special   --       Toxic Poison Status   --