How do you capture Darkrai?

Go into Mt Cornet the Hearthrome City side nd go up the mountain.
But before facing Daigla you must team up with your rival and face two commanders and Cyrus. THEN you can face diagla.

Go to a Nintendo Event or cheat to get the item Membership Pass. Take that to the locked building behind the Canalave Pokemon center. You will fall asleep and appear on an island. Not to far away is a Lv 40 Darkrai ready for battle

Attend a Nintendo Event, or use an Action Replay to get one.

It is impossible to get him unless you go to some special event that happens in Japan. But there is a way to get him with a cheat device called a Action Replay. If you don�t you can buy one at GameStop/EB Games. I bought mine at Best Buy for $20. If you have an Action Replay here is the code to get him.

Note: This also works for Pokemon Pearl Version.

94000130 FCFF0000
B21c4d28 00000000
B0000004 00000000
0000aa3c EDB88320
2000aa68 00000008
D2000000 00000000

If the code is entered correctly start your game and go fly to Canalave City. Now once you arrive press the L and R buttons at the same time. Now go to the Poke� Market and inside there will be a man in green. He will give you a Members Card. Now leave the market and go to the very top of the city and the one house you could not enter is now accessible. Once you go inside you will man will let you use the single bed inside. You go in the bed and fall asleep. Then when you wake up you will be on a island called Newmoon Island. Search the area and once you go inside the forest area there inside hover above some water is Darkrai. Save before you battle, you know incase you screw up or something (because this is the only time you can do it, if you try to do the cheat again it wont work). Talk to Darkrai and he will battle you. He should be at Level 40. Once you capture him return back to the ship and congratulations you have captured Darkrai. Note: Don�t worry he is not a glitch Pokemon or nothing he works and acts as a normal Pokemon would.

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My Darkrai's nature was this
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Nature: Serious
Likes to trash about
Happily Eats Anything
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I hope this information helped you and all you Darkrai fans out there. I happen to like Darkrai myself, though he is not my favorite Pokemon, he is still awesome.

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Oh by the way my names Vincent Vagasky and if you want to trade or battle me my trainer card is this

Trainer Name: Dawn
Friend Code: 1160-6686-1141
My Main Team: Feraligatr (Male), Arbok (Male), Gardevoir (Female), Mewtwo (Genderless), Dialga (Genderless), Moltres (Genderless)

I change my team sometimes but for the most part that�s my team
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Assuming you cheated to get the Member's Pass, or you actually flew to Japan to attend a Nintendo Event to obtain one, and you're standing in front of Darkrai...
Just start using Dusk Balls. From seeing pictures, it looks like he's in an enclosed forest... So Dusk Balls will get their advantage.
Weaken him first, of course, and being paralyzed, asleep, or frozen will work even more to your advantage. You'll have him in no time.

If you don't know how and what to do to get him... Well, from my first sentence, you can tell that cheating or long-travelling is required. At least until the Nintendo Events become available in the United States...

If you get a member card from the events or action replay then go to the Canalave harbor inn.

Or... if you have a action replay, then use the walk anywhere code and ask the Canalave sailor to take you to Fullmoon Island, and then Keep walking left (off the island) until you get to Newmoon island and catch battle Darkrai.

You need to go to the event in Japan, Organise a trade over WiFi, Cheat to get Darkrai or Cheat to get the Members pass in order to get to New Moon Island where Darkrai is found

Use the dark world glitch, go to the first door of the elite four and use surf. You can catch darkrai and a whole load of other pokemon. You have to fly or dig to get out of there.

All I know is that you use the action replay and go to full moon island then keep walking to the right and your on the island that darkrai is on and it's just like how you captured cresselia by going into the trees and you see darkrai! Save right before you battle him and try to catch him! But hes really hard to catch so I suggest you use a master ball.

This is an event that is currently happening, you need Wi-Fi for it, I swear it works, I got a FREE Darkrai this way.

Go to your Wi-FI settings, select the your going to use, & where it sais 'Auto Obtain DNS" click "No" & edit it. Enter this DNS code: 204 045 029 054. Then, press back until you are at the starting Load your save, & go to the GTS. Walk into the trading place, & connest to Wi-ZFi.You will need to try to connect a lot of times, I kept getting errors. But if you are patient, you will walk in & recieve levle 50 Darkrai for free. OT: Almia, fateful encounter at Pokemon Ranger, moves are double team, dark void, dark pulse, & shadow ball. You may get a communication error, that is OK. Or, if you put in this code in the DNS.(99.41.98.43.) you will recieve a gamestop Celebi. Enjoy!There are also codes for other Pokemon, like Deoxys & Jirachi.