https://www.polygon.com/pokemon-go/2018/7/14/17572102/pokemon-go-celebi-how-to-catch-pokemon-go-fest-2018

Pokémon Go Fest 2018’s surprise new Pokémon is Celebi, the latest and last second-generation mythical monster to arrive in the game.

Unlike last year’s event, when a variety of network issues led Niantic to gift everyone the legendary Pokémon Lugia, attendees actually have to work to capture Celebi. And they have to work hard — I’m nowhere near unlocking one myself, and I’ve been here for several hours.