Pokémon UNITE is continuing to add new content, including new playable characters and in-game items, on a regular basis. Read on below to learn more:
Source: Official Pokémon UNITE website
Gyarados will be added to Pokémon UNITE as a playable character on January 25
Pokémon Blog 
5 thoughts on “Gyarados will be added to Pokémon UNITE as a playable character on January 25”