The third and final member of the Regi trio, Regirock, will be taking over legendary raids from today in Pokémon Go.
Regirock will only be in legendary raids until Sept. 20, however, so don't delay trainers. Most legendary raid Pokémon don't show up for a while after they leave raids, so this might be your only chance to grab Regirock until it appears again.
Regirock's inclusion signals the end of Registeel in the legendary raids and is one of the final Hoenn Legendary Pokemon to be added to the game. Only Deoxys and Jirachi remain from the legendary pool of Pokemon from the Hoenn region.
Related: How to catch Regirock in Pokémon Go
Regirock first appeared in Pokémon Ruby and Sapphire for the Game Boy Advance and was one of three Pokémon that laid dormant under the earth, waiting to be found. Trainers could only unlock the ability to capture these trainers by having two unique Pokémon in their party while in front of a secret stone tablet—so the method to capturing Regirock in Pokémon Go is a lot easier than that.
In order to catch Regirock, trainers will need to band together to challenge the raid for the best chance of beating the powerful Pokemon. If a team successfully beat Regirock, they will be given a small amount of Pokéballs to try to catch it.
If you fail, you will need to try to find another legendary raid to challenge Regirock and try all over again.