Niantic has confirmed that Regigigas, the Colossal Pokémon, is appearing in EX Raids starting this month in Pokémon GO. According to the developer, EX Raid Battles initiated by the EX Raid Passes that were distributed on the day of November 9 or later are tied to Regigigas, giving players another chance to encounter the Colossal Pokémon and officially add it to their team.
Source: Official Pokémon GO blog
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