How do you unlock Darkrai on Pokemon Battle Revolution?

To unlock Darkrai in Pokémon Battle Revolution, you must have a Nintendo DS and a copy of Pokémon Diamond, Pearl, or Platinum inserted into the DS slot of the Wii. Then, you must visit the Battle Tower and speak to the man standing next to the counter. He will ask if you want to receive a Darkrai. If you accept, you will receive a Darkrai and it will be added to your Battle Revolution party.