http://www.newsweek.com/pokemon-go-update-shiny-geodude-grimer-1120681

The latest Pokémon Go update is live and brings a bunch of changes to the game including possibly new Shiny Pokémon, Raid Battles and more.

Niantic announced that the Legendary Bird Trio (Moltres, Zapdos and Articuno) will once again appear in Raid Battles for a limited time, and then will be replaced by Mewtwo. Prior to this update, Mewtwo was only available to catch if a player received an EX Pass.