The Master Ball is finally coming to Pokémon Go in the Season 10 finale
As part of the finale for Season 10: Rising Heroes, Niantic is finally introducing the Master Ball to Pokémon Go. Long since uncovered via data mining, the Master Ball works the same as in the main series games and guarantees capture of whichever Pokémon you use it on.
To get your hands on a Master Ball, you must claim the last Special Research of Season 10 between the 22nd May and the 1st June. Completing the research will result in a Master Ball reward. Future Master Balls will be available, but obtaining them will seemingly remain a special reward for certain tasks.
Recent data mining has also suggested that catch rates, in general, might have been decreased, making the Master Ball all the more valuable for difficult-to-capture Pokémon such as powerful legendaries. Likely much to the chagrin of plenty of players after a string of fairly unpopular moves from Niantic about the game, such as changes to Raid Passes and Remote Play in general.