How to Find the Eon Duo in Pokémon Scarlet and Violet

Latias and Latios, popularly known as the Eon Duo thanks to their title on the Pokédex; they were first introduced in the third Generation; while technically being the same Pokémon but female and male respectively, Latios has better attack and Special Attack stats, while Latias has better Defense and Special Defense.

To find them in Pokémon Scarlet and Violet, you have to first complete the DLC story The Hidden Treasure of Area Zero, then talk with Snacksworth by the entrance of Blueberry Academy; he will give you a Treat at random for completing Solo and Group Blueberry Quests, depending on your game version, you have to complete solo quests for one and Group Quests for the other.

Both Pokémon have the Levitate ability, making them immune to Ground type moves.

Latias

Latias will appear on a beach south of South Province Area Four, directly south of the watchtower; she has moves more focused on having the same defenses as your Pokémon, stat wise, and type-wise.

Latios

Snacksworth's story talks about ending up in a secret spot on the northeast; Latios will be next to a small lake surrounded by cliffs and a tree in the middle; this lake is southwest of Team Star's Fighting Crew's Base; he has damaging moves focused in side effects, such as lowering your Sp. Defense, make you flinch or Paralyze you.