It's on New Moon Island
You dont catch Darkrai in Pokemon Pearl. You can catch it in Pokemon Platinum at level 40.
Unless you go to fullmoon island, you can't get darkrai
Darkri is on new moon island, you can get there by cheating or a Nintendo special event.
You have to go to Fullmoon Island. Then use the walkthrough cheat on the right side and walk across the water until you get to another island. You will find Darkrai on that island.
Cresselia's island and Darkrai's island.
you catch him
you get event Pokemon then go cacth creselia and go to canalave city walk to the harbor inn and stay there for a night the you will have a dream you will be on a island and walk up to a puddle and darkrai will be there
Shaymin and Darkrai. Search for pearl tweaking glitch on youtube.
Darkrai is a Pokemon from Generation IV, and Pokemon ruby is a game from Generation III , so you can only get darkrai in Pokemon Platinum, Diamond or Pearl
You have 2 Nintendo DS then send the darkrai (You have to have the mystery gift in diamond or pearl)
go to cresselia island and use walk thru wall cheat and walk right until see a island
its both darkrai or criselia