From Bulbapedia, the community-driven Pokémon encyclopedia.
Gateway Colosseum (Japanese: ゲートコロシアム Gate Colosseum) is the first Colosseum in Pokémon Battle Revolution. The battle theme is Rental battles like in the Battle Factory in Pokémon Emerald. The Colosseum leader is Colosseum Master Joe. Like most other Colosseums, there are 7 battles in all.
Gateway Colosseum floats at the entrance to Pokétopia and is lit by bright neon lights. All battles here are depicted as happening at night.
The battle theme, Rental Battle, requires one to use only Rental passes in this Colosseum. Custom passes are barred; you may not use your own Pokémon here. However, once you beat all 7 battles, you get to keep the Rental Pass you used. At the start of the game, there are two Rental Passes to choose from, the Red Rental Pass and the Blue Rental Pass; you can return after claiming victory to challenge Rank 2 and earn the other Pass. Similiarly, after you beat Waterfall Colosseum
you can return to Gateway Colosseum and unlock the Purple Rental Pass and the Green Rental Pass. After beating Sunny Park Colosseum
, you may return to Gateway Colosseum and challenge it two more times to win the final Rental passes, the Grey Rental Pass and the Yellow Rental Pass.
After you beat the game, you are allowed to participate in a Battle Swap after each battle. This involves permanently trading one of your Pokémon for one of the opponents Pokémon. This can only be utilized using the Level 50 All rule. This battle theme is called "Trade Battle".
Beating Gateway Colosseum for the first time in Level 30 Open mode gets you a Bronze Badge, a custom Battle Pass with Gateway Colosseum in the background, and 280 Poké Coupons. Beating Gateway for the first time in Level 50 All mode unlocks 37 pieces of gear in the shop.
Also, the default mode of battle here is Single Battle. An option to change this to Double Battle is made available after beating Rank 1 for the first time.
The Pokémon and Trainers are not set, except during the first time you battle there, at Rank 1 Level 30 Open, and the first time you battle using the Level 50 All mode, Rank 1 Level 50 All. The Trainers, and the Pokémon they have, go as the following during Level 30 Open, Rank 1:
The Trainers, and the Pokémon they have, go as the following during Level 50 All, Rank 1: