https://www.gamespot.com/articles/last-chance-to-catch-latest-pokemon-go-legendary-h/1100-6455604/

The latest Legendary Pokemon in Pokemon Go, Ho-Oh, has been appearing in Raid Battles across the globe for the past two weeks, but it won't be around for much longer. The rainbow-colored Pokemon will only be available until December 14, making this your last day to catch one if you haven't yet.

Ho-Oh was unlocked in Pokemon Go late last month, following the successful completion of the game's Global Catch Challenge. The event tasked players with capturing 3 billion Pokemon worldwide. Players managed to surpass that goal just prior to the deadline, unlocking the rare Pokemon Farfetch'd for a brief time (Kangaskhan was also briefly unlocked in east Asia).