The Eon Pokémon from Ruby and Sapphire soar back into Pokémon Go; Latias and Latios are coming back to raids in a new upcoming Special Raid Weekend.
Starting on Jan. 24, at 1pm Pacific Standard Time, Latias and Latios will begin appearing in five-star raids. Latias and Latios are both psychic and dragon-type Pokémon, meaning they are weak against a ghost, dark, fairy, bug, and other dragon-type Pokémon. The Pokémon Go Blog suggests using Pokémon like Rayquaza, Dialga, Tyranitar, Togekiss, and Mamoswine against them when players encounter them.
The event is currently schedule to end on Jan. 27, at 1pm PST.
— Pokémon GO (@PokemonGoApp) January 16, 2020
Latias and Latios are a pair of Legendary Pokémon that were introduced back in Gen. III. They have a similar appearance, with their main difference being their colors and gender. Latias is red and female, whereas Latios is blue and male. They are dubbed the Eon duo by fans as they are both referred to as the Eon Pokémon, which is a reference to the term Aeon.
They were also the stars of the fifth animated Pokémon movie, Pokémon Heroes. In the movie, they are introduced as brothers and sisters, which would explain their similar appearances and close bond.