The legendary Pokemon Rayquaza is available in Pokemon GO in Raid Battles for a limited time, alongside it’s counterparts Groudon and Kyogre. The event will run until March 5, 2018.
Depending on which Pokemon is defeated more, Pokemon that prefer to hatch in a certain type of weather will hatch easier. For example, defeating Rayquaza more than Groudon and Kyogre will let Pokemon like Bagon hatch easier.
Pokemon GO is currently available for iPhone and Android.