Remember that this particular Decidueye can only be caught once per save file. After that, you can still participate in Tera Raid battles, but you will get different rewards.
This Pokemon will be available from March 17-19 in Tera Dark Crystal Raids and again from March 24-26. This Decidueye is not usually seen in the Paldea region, has Flying as Tera Type as well as Mightiest Mark.
If you’re not familiar with Tera Raid Battles in Violet and Scarlet, this is where trainers work with three other trainers to defeat the mighty Tera Pokémon before time runs out. Each raid event is different, and the Pokémon comes with rare Tera types.
In related news, The Pokémon Company announced last week that it will be releasing a new update for Scarlet and Violet sometime in late April.