Season 15

Season 15 of GO Battle League, also called GO Battle League: Hidden Gems, lasted from June, 2023 to September , 2023. It is preceded by Season 14 and succeeded by Season 16. This GO Battle League Season ran concurrently with Hidden Gems.

Formats
Summer Cup: Great League Edition: 1,500 CP limit. Only Normal-, Fire-, Water-, Grass-, Electric-, and Bug-types allowed.

Summer Cup: Ultra League Edition: 2,500 CP limit. Only Normal-, Fire-, Water-, Grass-, Electric-, and Bug-types allowed.

Element Cup: Little Edition: 500 CP limit. Only Fire-, Water-, and Grass-types allowed. Only Pokémon that are able to evolve and have not evolved even once are allowed.

Single-type Cup: Great League Edition: 1,500 CP limit. Only single-typed Pokémon allowed. Cresselia and Defense Deoxys are banned.

Retro Cup: Great League Edition: 1,500 CP limit. Dark-, Steel-, and Fairy-types are banned.

Fossil Cup: Great League Edition: 1,500 CP limit. Only Water-, Rock-, and Steel-types allowed.

Great League Remix: 1,500 CP limit. Venusaur, Alolan Ninetales, Noctowl, Lanturn, Azumarill, Umbreon, Skarmory, Swampert, Pelipper, Sableye, Medicham, Altaria, Walrein, Registeel, Defense Deoxys, Bastiodon, Froslass, Galarian Stunfisk, Trevenant and Obstagoon are banned.

Fantasy Cup: Ultra League Edition: 2,500 CP limit. Only Dragon-, Steel-, and Fairy-types allowed. Galarian Stunfisk and Cobalion are banned.

Catch Cup: Hidden Gems Edition: 1,500 CP limit. Only Pokémon caught during Hidden Gems allowed.

Rewards
Basic Premium
 * Rank 5: Mysterious Item
 * Rank 10: 750 (Basic) / 1500 (Premium) Stardust
 * Rank 15: 1 (Basic) / 2 (Premium) Rare Candy
 * Rank 19: Pokémon Encounter
 * Other ranks:

Stardust

The random items can include:
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Reaching rank 19 awarded:

Reaching Ace rank and above awarded avatar items and an avatar pose inspired by Clay from Pokémon Black and White.

Clay-Style Hat could also be obtained from GO Battle Day rewards.

Pokémon
Guaranteed first Pokémon encounters:
 * Excadrill: rank 1 (one only)
 * Skwovet: rank 6 (one only)
 * Axew: Ace rank
 * Gible: Veteran rank
 * Goomy: Expert rank
 * Pikachu Libre: Legend rank (one only)

Tier 5 Raid Bosses could be obtained starting at rank 20 during their time in raids.

End-of-Season rewards

 * (rank 19 or above)

Timed Research
GO Battle League Timed Research is for the GO Battle League Season 15. A Ticket for this Timed Research was available in the in-game shop at no cost. This research was automatically added to players who had the ticket in previous Season. Each part of the Timed Research had the same requirements, with the only difference being the rewards for completing each part.

GO Battle Weekend: Clay
GO Battle Weekend: Clay took place from July, 2023, 12 a.m. local time to July , 2023, 11:59 p.m. local time. Master League Premier and Single-type Cup were available during this GO Battle Weekend.

Attack updates
These Attack updates went live at the start of the Season:

Attack changes

 * Icicle Spear: Base power increased from 60 to 65 in Trainer Battles.
 * Poison Fang: Base power increased from 40 to 45 in Trainer Battles.
 * Rollout: Base power increased from 4 to 5 in Trainer Battles.
 * Mud Bomb: Base power increased from 55 to 60 in Trainer Battles.
 * Seed Bomb: Base power increased from 55 to 60 and energy cost increased from 40 to 45 in Trainer Battles.

Attack availability
Some Pokémon received new Attacks to their standard Attack pools: