Pokémon GO’s Twilight Trails season begins Sept. 8, 2026, bringing Mega Evolution to the GO Battle League for the first time and introducing new Mega Edition formats across the Great League, Ultra League and Master League. Mega-Evolved Pokémon will be eligible in the Great League: Mega Edition, Ultra League: Mega Edition and Master League: Mega Edition, while select Pokémon will gain additional Charged Attacks as part of the new battle system. The season runs through Dec. 1 and will feature special competitions including the Willpower Cup, Retro Cup, Mega Color Cup, Little Cup, Fantasy Cup, Mega Halloween Cup, 2026 GO LAIC Cup and Mega Catch Cup. Trainers can earn guaranteed encounters with Toxtricity (Low Key Form), Dondozo, Kingdra, Duraludon and Pikachu Libre, with additional reward encounters including Mimikyu, Cramorant, Morpeko and other Pokémon. GO Battle League: Twilight Trails will also introduce battle-focused Timed Research, new Ryme-inspired avatar items and a daily battle limit of up to 50 battles during GO Battle Thursday, while dozens of attacks receive balance changes that could significantly impact the Pokémon GO PvP meta.
Source: Official Pokémon GO blog
Nintendo & Pokémon Blog 