use a master ball
Darkrai can be caught in any kind of Poke Ball, but Ultra Ball has 4x the catch rate by itself, which is pretty high.
It actually isn't so special; a Premier Ball's catch rate is the exact same as a regular Poke Ball.So, it's like a Poke Ball that costs 10 Poke balls with a different entrance effect.
poliwag?
You can only obtain Darkrai through Poke Transfer in Pokemon White/Black.
great ball
when you apply the darkrai cheat to poke park you have to go to the haunted zone and go inside the haunted house and go near the piano where mismaguis is and look around and darkrai should be there
use poke balls on it
A poke ball costs 200 poke's (in game money) A great ball costs 600 poke's An ultra ball costs 1200 poke's But you can't by a master ball but you get one just by playing.
You'll need to either:Trade for it.Transfer it using the Poke Transfer.
You buy it at any poke mart
When you beat the Champion go to Steven's house. There will be a poke ball. There will be a Beldum in the poke ball.
Lower its HP until it's at the Red marker. Find it again, then put it to sleep with a fast Pokemon. (Suggest darkrai) Get a variety of poke balls and throw them at the Pokemon to try and catch it. If you have used poke balls a lot of turns then throw a TIMER BALL.