Niantic has announced the details for the GO Battle League Season 9 update. Below are all the details.

GO Battle League: Season 9 Update

Trainers, GO Battle League Season 9 is set to kick off! Your ranking at the end of this season will be more important than it ever has, so make sure to start your climb early! As the season progresses, we’ll have more to share on how this season’s results will impact things going forward—so stay tuned!

Now, let’s get into what you can expect during GO Battle League Season 9!

Season 9 Start Date, Rank Resets, and End-of-Season Rewards

GO Battle League Season 9 will start on Monday, August 30, 2021, at 1:00 p.m. PDT (GMT −7).

The following will occur at the beginning of the season.

• End of season rewards will be available on the battle screen.
• Your GO Battle League rank will be reset.
• Rank-up requirements will remain the same as in Season 8.

Season 9 Schedule

The following leagues will begin and end at 1:00 p.m. PDT (GMT −7) on the dates listed below.

What’s new in Season 9?

GO Battle Days
To allow more Trainers to participate, GO Battle Nights will become GO Battle Days from GO Battle League Season 9 onward!

Bonuses

• The maximum number of sets you can play per day will be increased from five to 20, for a total of 100 battles.
• 4× Stardust from win rewards (this does not include end of set rewards and will not stack with the 3× Stardust bonus on November 20).

Dates and Times
Saturday, September 18, 2021, from 12:00 a.m. to 11:59 p.m. local time: The Ultra League and Ultra League Remix will be active.
Monday, November 1, 2021, from 12:00 a.m. to 11:59 p.m. local time: The Ultra League, the UL Premier Classic, and the Halloween Cup will be active.
Saturday, November 20, 2021, from 12:00 a.m. to 11:59 p.m. local time: The Master League, ML Premier Classic, and a cup chosen by Trainers will be active.

Season 9 rewards

Guaranteed rank-up encounters
You can encounter the following Pokémon once per season at the designated ranks. At rank 1, you’ll be guaranteed to encounter one of the Pokémon that Galar Champion Leon is known to use!


: If you're lucky, you may find a shiny one!
: Veteran Rank
: Expert Rank
: Legend Rank

Standard encounters
You can encounter the following Pokémon as win rewards throughout the season at the ranks shown in the image below.


: If you're lucky, you may find a shiny one!
: The Pokémon currently appearing in five-star raids has a chance of appearing as a reward encounter after you reach Rank 20.
: Veteran Rank
: Expert Rank

Avatar items and other rewards

Pikachu Libre avatar items will be rewarded to Trainers who reach Rank 3.


Trainers will be able to earn avatar items and a pose inspired by the champion of the Galar region, Leon, who first made his debut in Pokémon Sword and Pokémon Shield!

• At Ace rank, you’ll receive the Reigning Champion Sport Glove.
• At Veteran rank, you’ll receive the Leon’s Look Sport Cap.
• At Expert rank, you’ll receive the Reigning Champion Sport Shorts.
• At Legend rank, you’ll receive the Reigning Champion Sport Top.
• Midway through season 9, Leon’s iconic pose will be added as a reward for Trainers who reach Legend rank.

At Rank 19, you’ll receive an Elite Charged TM, and you’ll also receive an Elite Fast TM as an end-of-season reward.

Cups

You can look forward to the following cups this season.

Great League Remix

The 20 Pokémon most used by Trainers Ace rank and up in the Great League will not be allowed in the Great League Remix.

The following Pokémon will not be allowed.

Ultra League Remix

The 10 Ultra League Pokémon most used by Trainers Ace rank and up in the Ultra League will not be allowed in the Ultra League Remix.

The following Pokémon will not be allowed.


Little Jungle Cup

• Pokémon must be at or below 500 CP to enter.
• Pokémon do not need to be able to evolve to enter.
• Only Normal-, Grass-, Electric-, Poison-, Ground-, Flying-, Bug-, and Dark-type Pokémon are permitted.
• Shuckle and Smeargle are not permitted.

Halloween Cup

• Pokémon must be at or below 1,500 CP to enter.
• Only Poison-, Bug-, Ghost-, Dark-, and Fairy-type Pokémon are permitted.

Special Cup: Players' choice
We’re interested to hear which prior special cup you’d like to see return this season! Stay tuned for a poll on Twitter later in the season to determine which cup will be held.

New attacks

Weather Ball: A new, low energy cost Normal-type Charged Attack.

• Trainer Battles: 55 Damage
• Gyms and raids: 55 Damage

Attack changes

Weather Ball: Weather Ball is currently a little too efficient as a low-energy Charged Attack. As a result, we’re toning down its damage just a tad.

• Trainer Battles: 60 → 55 damage
• Gyms and raids: 60 → 55 damage

Crunch: We’re adding an effect to this move when it’s used in Trainer battles to tie in with its effect in the core Pokémon RPGs.

• Trainer Battles: Now has a chance of lowering the opposing Pokémon’s Defense.

Zap Cannon: We’re adding an effect to this move when it’s used in Trainer Battles to tie in with its effect in the Pokémon RPGs. We hope this will provide Pokémon like Zapdos, Regirock, Magnezone, and Porygon-Z a chance to shine.

• Trainer Battles: Guaranteed to lower the opposing Pokémon’s Attack.

Scald: We’re lowering the energy cost of this Charged Attack and adding an effect to this move when it’s used in Trainer battles to tie in with its effect in the core Pokémon RPGs.

• Trainer Battles: Energy cost decreased and now provides a chance of lowering the opposing Pokémon’s Attack.

Feather Dance: We’re increasing the energy cost of this Charged Attack slightly to make it harder to use as often.

• Trainer Battles: Energy cost increased.

Megahorn: We’re giving Megahorn a slight increase in damage to boost Nidoking’s, Heracross’s, and Escavalier’s high-cost Charged Attack options.

• Trainer Battles: 100 → 110 damage

Attack availability updates

Source: https://pokemongolive.com/post/gobattleleague-season9