Pokémon Colosseum

The Double Battle Institute is the first Pokémon Colosseum you reach.
It is located in Amberdale.

However, the challenge of the facility can only be accepted after receiving the second gym badge.

In the Double Battle Insitute fights are held in 2 vs. 2.
While in easy mode you can use all your Pokémon, in hard mode you have to choose your two active Pokémon every round.

Plusle & Minun Cup
Unlocking: 2th gym badge
Level: 18 - 24
Prices: Fast Ball, Level Ball, Lure Ball, Heavy Ball, Love Ball, Friend Ball, Moon Ball

Solrock & Lunatone Cup
Unlocking: 5th gym badge
Level: 36- 42
Prices: Mental Herb, White Herb, Power Herb, Focus Sash, Focus Band,
Absorb Bulb + Snowball + Cell Battery

Espeon & Umbreon Cup
Unlocking: 7th gym badge
Level: 55 - 60
Prices: Macho Brace, Power Weight, Power Bracer, Power Belt, Power Lens, Power Band, Power Anklet

The Storage Hall Colosseum is located in Granitedeep City.

In the process of the D&D sidequest "Hopeless geniuses" you will get access to the Storage Halls Colosseum, where you can challenge the Sableye Cup right away.

To start the quest, talk to D&D in the top left house in Granitedeep City.

The tournament is held in single battles.
In easy mode you can take your full team into the battles, in hard mode you have to choose 3 Pokémon to battle before each tournament round.

Sableye Cup
Unlocking: Available immediately
Level: 26 - 31
Prices: Red Shard, Blue Shard, Green Shard, Yellow Shard

Houndoom Cup
Unlocking: 6th gym badge
Level: 42- 47
Prices: HP Up, Protein, Iron, Calcium, Zinc, Carbos

Drapion Cup
Unlocking: 8th gym badge
Level: 60- 65
Prices: Fire Stone, Water Stone, Thunder Stone, Leaf Stone, Moon Stone, Sun Stone, Dusk Stone, Dawn Stone, Shiny Stone, Ice Stone