HiGame

Pokemon players can now add two more mythical monsters to their collections in Pokemon Brilliant Diamond and Shining Pearl. After downloading the recent 1.3.0 update, you'll be able to obtain items that lead to encounters with Arceus and Darkrai, making this your first opportunity to get the mythical Pokemon in the games.

How to catch Arceus
Before you can encounter Arceus in Pokemon Brilliant Diamond or Shining Pearl, you'll first need to have entered the Hall of Fame and obtained the National Pokedex in the remakes, as well as cleared all of the main story missions in the Pokemon Legends: Arceus game.
Once you've met those requirements, return to your bedroom in Twinleaf Town and obtain the Azure Flute. Take the item to Spear Pillar atop Mount Coronet and you'll trigger an encounter with Arceus.

How to catch Darkrai
To encounter Darkrai, you'll need to have the Member Card, which will be distributed via Mystery Gift between April 1 and April 30. Once you've obtained the Member Card, you'll gain access to the locked inn at Canalave City. Upon entering the inn, you'll travel to Newmoon Island, where you'll encounter Darkrai.
You'll need the Member Card, which is being distributed via Mystery Gift between the new moons, to encounter Darkrai.

more...