The Wyrdeer is an evolution of the Stantler, and is native to the Hisui region in Pokemon Legends Arceus.
As for Pokemon Legends Arceus itself, the game will be released on January 28, 2022 on the Nintendo Switch.
As a Water/Ghost-type Pokémon, Basculegion’s evolution in Pokemon Legends Arceus is triggered when a Basculin is possessed by the souls of its dead companions.
Two that were revealed on the August 18, 2021 stream were evolutions of existing Pokemon that will appear in Pokemon Legends Arceus–Wyrdeer and Basculegion.