Pokemon GO players can finally catch Mewtwo in the game's first Exclusive Raid Battle. At an event in Yokohama, Japan tied to the Pokemon Invasion, one of the final parts of the Pokemon GO Fest meant to celebrate the game's first anniversary, thousands of players banded together to take down Mewtwo, and many of those players were able to catch a Mewtwo of their own. Thanks to that concerted effort, Mewtwo will be appearing worldwide for an undetermined amount of time, but you can only have a chance at Mewtwo if you qualify for an Exclusive Raid Battle where one will appear.
Exclusive Raid Battles work quite differently from normal ones. A normal Raid Battle is open to any Pokemon trainer of a high enough level, can appear at random at any given time, and gives trainers the chance to get into a battle quickly, teaming up with whoever happens to be nearby. Exclusive Raid Battles, however, are only open to trainers who have recently completed a normal Raid Battle at the gym where the Exclusive Raid Battle will be taking place. Qualifying trainers will be given advance notice that an Exclusive Raid Battle will be starting soon, where it will take place, and when. Niantic did not say exactly how long trainers would have between getting the notification and having to report for the battle, but the company's press release said that trainers would have "ample time" to get together with other trainers, stock up on items, and sort out their Pokemon team. Additionally, winners may also receive an egg that could hatch powerful Pokemon, but Niantic did not say what Pokemon were in the running.
The emergence of Mewtwo and the unveiling of Exclusive Raid Battles is one of the last bastions of the ongoing Pokemon GO Fest. Articuno, Zapdos, Moltres, and Lugia have been appearing worldwide in random Raid Battles during the course of the event, but according to Niantic's press release, those legendary Pokemon won't be around forever. Trainers have until August 31 to catch all four legendary Pokemon, or they won't get another chance until those Pokemon surface again, and there was no word on when that may be