In each generation, there is typically at least one group of Legendary Pokémon that form a trio. Each Trio is seemingly subject to another Legendary Pokémon.
- Regice, Regirock and Registeel – The Legendary Golems, led by Registeel and ruled by Regigigas.
- Groudon, Kyogre and Rayquaza – The Weather Trio, led and ruled by Rayquaza itself.
- Uxie, Azelf and Mesprit – The Lake Trio, led by Azelf and ruled by Arceus.
- Dialga, Palkia and Giratina – The Creation Dragons, led by Giratina, and ruled by Arceus.
- Reshiram, Zekrom and Kyurem - The Tao Dragons, led and ruled by Kyurem itself.
- Cobalion, Terrakion, and Virizion - Three Pokémon based on the titular characters of the novel The Three Musketeers. Out of these swords of justice, Cobalion is the oldest and wisest and is considered their leader.
- Keldeo, Meloetta and Genesect: The random event trio
- Tornadus, Thundurus, and Landorus - Based on three Japanese gods known as kami, with Tornadus based on Fujin, the god of wind, Thundurus on Raijin, the god of thunder, and Landorus on Inari, the fertility god. Landorus is the master of this trio.
Some of the remaining Legends fit into pairs, namely:
- Mew Duo: Mew and Mewtwo
- Tower Duo: Lugia and Ho-Oh
- Eon Duo: Latias and Latios
- Lunar Duo: Cresselia and Darkrai
- Mega Duo: Mega Mewtwo X and Mega Mewtwo Y
- Sea Guardians: Manaphy and Phione
- Starting with Rayquaza, the majority of the third mascots had Dragon in their typing and forms. Necrozma almost broke the chain until Ultra Necrozma was introduced.