Eon duo is a fan term for the Legendary duo that consists of the Eon PokémonLatias and Latios. They are also referred to as Lati@s (as the symbol "@" looks like an "a" inside an "o") or the Lati twins.
In Pokémon Ruby, Omega Ruby, and Emerald, if the player chooses Latios to roam Hoenn, with an Eon Ticket the player can go to Southern Island, where they will encounter Latias. In Pokémon SoulSilver, if the player has an Enigma Stone, Latias can be found and captured in Pewter City.
In Pokémon Sapphire, Alpha Sapphire, and Emerald, if the player chooses Latias to roam Hoenn, with an Eon Ticket the player can go to Southern Island, where they will encounter Latios. In Pokémon HeartGold, if the player has an Enigma Stone, Latios can be found and captured in Pewter City.
Latias and Latios debuted in Pokémon Heroes: Latios & Latias, where they serve as the guardians of Alto Mare and protectors of the Soul Dew. Latias also displayed the ability to shape-shift into humans such as Alto Mare resident Bianca. They were targeted by thieves Annie and Oakley, who desired possession of the Soul Dew. Latios was eventually captured by them, forcing Latias to enlist the assistance of Ash, who she seemed to have a crush on. Though they were able to rescue Latios and thwart Annie and Oakley's plans, the villainous pair's actions still endangered all of Alto Mare, forcing Latios to sacrifice himself and turn into the new Soul Dew, just like his father did in the past.
A Latias appereared in The Road Most Traveled!, where Ash encountered an injured Latias and helped her to recover, even saving her from being captured by Team Rocket. At the end of the episode, she started to secretly follow Ash. In Rocket Revengers!, she revealed herself to him and showed him a vision of a Latios in danger. After Latios had been saved in the next episode, Latias bid Ash farewell and journeyed to Alto Mare with Latios.
Pokémon Omega Ruby and Alpha Sapphire Animated Trailer
Latias and Latios Cards listed with a blue background are only legal to use in the current Expanded format. Cards listed with a silver background are legal to use in both the current Standard and Expanded formats.