Legendary Trios in Pokémon have existed since the first Generation with the iconic bird trio--Articuno, Zapdos, and Moltres. These trios have been consistent in almost every Generation of Pokémon with some of them often being the mascots of the Pokémon game like Ruby, Sapphire, and Emerald with their mascots being Groudon, Kyogre, and Rayquaza respectively.
These trios contain some of the most epic Pokémon ever. Many of the trios have even received some makeovers by receiving new forms. For some, these were Mega Evolutions and for others have received regional variants that give the Pokémon brand-new typings that make them feel like completely new Pokémon.
11 Lake Guardians Trio
The Lake Guardians Trio are featured in the video games taking place in Sinnoh like Diamond & Pearl. Each of these Legendary Pokémon serves as a guardian for their respective lake. Most trios usually consist of Pokémon of various different types, but these three are all Psychic-type.
However, each one of these Pokémon does have a couple of moves that are exclusive to them. Azelf has two Fire-type moves that only it can learn, Flamethrower and Fire Blast. Uxie focuses on a couple of powerful Grass-type moves like Giga Growth and Solar Beam. Then Mesprit has access to two Ice-type moves, Ice Beam and Blizzard.
10 Legendary Titans Trio
The Legendary Titans are Pokémon featured in the Hoenn video games, like some of the best Pokémon remakes, Omega Ruby & Alpha Sapphire. They are tremendous, powerful, and intimidating giants consisting of the Rock-type Regirock, the Ice-type Regice, and the Steel-type Registeel. These Legendary Pokémon are pure manifestations of their respective elements.
Their typings makes them some of the best Pokémon of their types. Overall, the trio is a fantastic group to use in a single team. However, Registeel is significantly the best of the three titans thanks to its many resistances as a Steel-type Pokémon. Regice on the other hand is at the lowest of the trio due to being a pure Ice-type Pokémon with many weaknesses.
9 Light Trio
Lunala is the Legendary mascot of Moon and Ultra Moon who is known as the "Moone Pokémon" and possesses a Psychic/Ghost-type. Solgaleo is a Psychic/Steel-type Pokémon called the "Sunne Pokémon" and is featured as the mascot Pokémon for Sun and Ultra Sun. While there is a clear dynamic in place between Lunala and Solgaleo, Necrozma comes in as a third entity.
Curiously, Necrozma seeks the light within Lunala and Solgaleo for itself to reach its true form. Fans get a glimpse of various forms of Necrozma which begins as a Psychic-type Pokémon that can absorb the types of Lunala and Solgaleo. However, Necrozma's true form is an epic gallant entity of a Psychic/Dragon-type.
8 Forces Of Nature Trio
The Forces of Nature are an epic trio that represents different aspects of nature and debuted in the Black & White games. Each of these Pokémon also has unique forms called Therian forms which give them new abilities and improve their performance in battle.
Tornadus, the "Cyclone Pokémon" is a representation of tornadoes and is a Flying-type Pokémon. Landorus is the "Abundance Pokémon" and a Ground/Flying-type Pokémon. It represents natural disasters involving the earth like earthquakes and volcanic explosions. Thundurus on the other hand is the "Bolt Strike Pokémon," an Electric/Flying-type Pokémon that represents thunderstorms.
7 Aura Trio
The Aura Trio is a group of Legendary Pokémon that made its initial appearance in Pokémon X & Y. This trio has an awesome representation of creation, destruction, chaos, and order. They aren't stated outright, but these themes appear in the Pokémon themselves. Xerneas, the Fairy-type mascot for Pokémon X, is less "creation" and more a representation of life.
Yveltal, the Dark/Flying-type mascot for Pokémon Y, on the other hand, is known for destruction and by default could be categorized as chaos too. Lastly is the Dragon/Ground-type Pokémon Zygarde, who represents order. Some of these themes are also seen more specifically in the Sinnoh legendary Pokémon.
6 Legends Of Galar Trio
The Legends of Galar make their appearance in Pokémon Sword & Shield. Rather than representing major concepts and themes, these Pokémon are more about heroic and villainous deeds with their lore often feeling like a classic traditional epic fantasy story. Zacian and Zamazenta are dog-like Pokémon who were heroic Pokémon that once took down Eternatus thousands of years ago.
Zacian and Zamazenta perfectly represent the heroes of a fantasy story with their respective sword, shield, and crown. Eternatus itself serves as a sort of Dark Lord Pokémon and has a terrifying and intimidating presence that causes the giant transformations of Dynamax.
5 Legendary Birds Trio
The Legendary Birds' first appearance was in Pokémon Red & Blue, however, they received amazing regional variants in Pokémon Sword & Shield's DLC. The trio are excellent representations of their elements and are drawn to areas containing these respective energies. Articuno is drawn to icy areas due to its typing in Kanto, but it's a Psychic/Flying-type in Galar.
Zapdos can be found near areas with high electricity in Kanto, and it can be seen running fast through the hills in Galar as a Fighting/Flying-type. Whereas Moltres is a Fire/Flying-type in Kanto and a Dark/Flying-type in Galar. While they are a trio, they seem to be subservient in some cases to Lugia which is wholly evident in one of the best Pokémon movies, Pokémon 2000.
4 Creation Trio
The Creation Trio are the popular legendary mascot Pokémon for Diamond, Pearl, and Platinum. Each of these Dragon-type Pokémon have played a part in the creation of the universe with the Mythical Pokémon Arceus presiding over all of them as the ultimate creator.
Dialga serves as the master of time and can manipulate it as it sees fit. Palkia on the other hand is the lord of space and can distort, create, and destroy dimensions in any manner. While these two Pokémon alone are incredibly powerful, neither of them are quite as strong as Giratina. Giratina is the banished Pokémon of the Distorted World and can control antimatter as it wills.
3 Tao Trio
The Tao Trio is an awesome trio of Pokémon that represent Yin and Yang. They're featured in Pokémon Black & White, as well as their sequels. Each of these Pokémon have their own elements alongside being some of the most powerful dragons ever. Zekrom is the Electric/Dragon mascot of Pokémon White and Reshiram is the Fire/Dragon mascot of Pokémon Black.
Kyurem on the other hand is the Ice/Dragon mascot of both sequels. It also has a form fused with Zekrom or Reshiram, depending on the game, where even more abilities are unlocked. However, it never loses its original typing. Unfortunately, there is no Kyurem that possesses a form involving both Zekrom and Reshiram, but it's not unlikely that it'll receive one someday.
2 Legendary Beasts Trio
The Legendary Beasts trio contained some of the best early Legendary Pokémon. Each one represents a different element by Ho-Oh. This happened upon their resurrection after dying from protecting people and Pokémon in the burning tower.
Each of these beasts is theorized to actually be an Eevee Pokémon due to each of them having the same typings as the original three Eeveelution Pokémon. However, there is a chance this is wrong and that fans might finally learn what their original forms were if a Legends: Celebi game really happens like people want.
1 Super-Ancient Trio
The Super-Ancient trio is easily the best trio so far to appear in Pokémon. Each one serves as a mascot for their respective games. Groudon is the Ground-type mascot of Ruby and Omega Ruby, Kyogre is the Water-type mascot of Sapphire and Alpha Sapphire, and Rayquaza is the Dragon/Flying-type mascot of Pokémon Emerald. This trio has long since been wrought in various battles.
Rayquaza is the strongest of the three and represents the skies. With its sheer strength, it is noted to putting a halt to Groudon and Kyogre's skirmishes. Kyogre is the second strongest and has the ability to expand the seas. Groudon on the other hand is the weakest, but it can still hold its own against the others and has the ability to expand the earth.