There are many legendary Pokemon that have appeared throughout the Pokemon series. With Pokemon GO currently having Kyogre and Groudon as tier five raid bosses for the Hoenn Celebration Event, many are able to once again witness the power behind these beasts.
Groudon was the box art legendary for the original release of Pokemon Ruby. It returned again as the center of a Pokemon game's box art with the remake of Pokemon Ruby, Pokemon Omega Ruby. Being a box art legendary, Groudon is the rival and counterpart to Kyogre of Pokemon Sapphire and Pokemon Alpha Sapphire.
As a Pokemon known for creating and expanding land masses, Groudon is a pure ground-type Pokemon. Similar to a mega evolution however, Groudon can undergo Primal Reversion to become Primal Groudon. This will change Groudon into a dual ground and fire-type Pokemon.
The Weather Trio
Groudon represents land of the Weather Trio Pokemon with Kyogre representing the ocean and Rayquaza representing the sky. Due to Groudon being a Pokemon that demonstrates its ability to expand landmasses it has been known to easily get into conflict with Kyogre.
Because of the amount of destruction that can arise from Groudon and Kyogre fighting, Rayquaza has been known on multiple occasions to get in the middle of the fights to stop it. This usually results in both Kyogre and Groudon returning to their homes in order to sleep and recover.
Pokemon Ruby, Pokemon Emerald, and Pokemon Omega Ruby
Being the mascot of Pokemon Ruby and Pokemon Omega Ruby, Groudon has a large role to play in them. With Pokemon Emerald also combining the plots of Pokemon Ruby and Pokemon Sapphire together, Groudon also plays an important role in that game as well.
No matter what in these games, Team Magma is planning on awakening Groudon in order to expand the world's landmasses. The creator of this plan is Team Magma's leader, Maxie. In order to enact this plan, Team Magma acquires the location where Groudon is sleeping as well as the Blue Orb (or the Red Orb in Omega Ruby).
After awakening Groudon, it goes on a rampage and causes all of the weather around the Hoenn region to go haywire. It is then discovered that Groudon has traveled to Sootopolis City. In Pokemon Ruby and Omega Ruby, players need to defeat or capture Groudon themselves in order to stop it from causing too much damage to the world in its angered state. With Pokemon Emerald however, the situation becomes a lot more complicated.
In Pokemon Emerald, Groudon confronts the also recently awakened Kyogre in Sootopolis City. With it being unwise for any normal person or Pokemon to get in between the two as they fight, the player trainer travels to the Sky Pillar and gets Rayquaza's help. After the trainer proves themselves to Rayquaza, it descends from the pillar to break up the fight and save the weather from causing too much damage. This causes Groudon to retreat and go back to sleep in Terra Cave.
The Pokemon Anime
Groudon has made multiple appearances throughout the main Pokemon anime and the Pokemon anime movies that have been released over the years. The most notable roles were in the main series during the Ruby and Sapphire arc.
With the anime being an adaptation of the games' plots, Team Magma and Maxie continue to work toward obtaining Groudon in order to expand the world's landmasses. In a twist however, Team Aqua captures Groudon while Team Magma captures Kyogre in order to foil each others' plans.
The two teams end up agreeing to a trade, but Shelly of Team Aqua sneaks onboard Team Magma's containment ship for Kyogre and frees it into the ocean. Groudon, however, is also eventually freed after being awakened by Ash's Pikachu, who was possessed by the Blue Orb. This leads to Groudon and Kyogre battling, with Groudon managing to defeat Kyogre. It then goes to a volcano to go back to sleep.
Unlike other depictions of Groudon like in the main games and spin-off games, Groudon in the anime is portrayed as having a protective side to it. This is because of Groudon's motivation for fighting Kyogre in the anime being mainly fueled by a desire to protect Monsu Island, which Kyogre was attempting to destroy with a tsunami.
Groudon also briefly appeared in the beginning of the Pokemon movie, Jirachi: Wish Maker. In it, a Team Magma scientist named Butler was working on making an artificial Groudon for the team, but couldn't without Jirachi. Once succeeding, the artificial Groudon goes on a mindless rampage with no desire other than destruction.
In the Pokemon movie, Hoopa and the Clash of Ages, Groudon appears once again with Hoopa Unbound controlling it and forcing it into its Primal Reversion state. It eventually breaks from its hypnosis and returns home with the other summoned legendary Pokemon.
Pokemon Mystery Dungeon
In Pokemon Mystery Dungeon: Blue Rescue Team, Pokemon Mystery Dungeon: Red Rescue Team, and Pokemon Mystery Dungeon DX, Groudon is a boss that is part of games' main story. During it, Groudon is awoken by the various natural disasters plaguing the world. This causes Groudon to start creating earthquakes out of anger.
With Groudon's earthquakes putting the lives of many Pokemon in danger, Alakazam, Charizard, and Tyranitar of Team A.C.T. go out to Magma Cavern to stop it. They are, however, defeated by the powerful Pokemon overcome by its anger. A new rescue team made up of Blastoise, Octillery, and Golem also attempt to challenge Groudon, but they are defeated as well.
In order to stop Groudon, multiple Pokemon Rescue Teams get together to form the ultimate rescue party for Team A.C.T. and calm Groudon down. Through them and the players' efforts, Groudon is eventually defeated. This helps calm Groudon down and helps stop the earthquakes.
After players beat the main story, they can return to Magma Cavern and challenge Groudon for a rematch. In this case, Groudon becomes even more powerful with the addition of being capable of Primal Reversion in Pokemon Mystery Dungeon DX. Once players take down Groudon in this rematch, they will be able to recruit this power house onto their rescue team.