As reported back in October, Arceus can be downloaded to Diamond, Pearl, and Platinum players starting tomorrow at America’s Toys R Us stores. Its attacks are Judgment, Roar of Time, Spacial Rend, and Shadow Force. It will be holding a Rowap Berry and is inside a Cherish Ball at Level 100. The event will last until next Sunday, November 15th.
When Arceus is taken to the Oreburgh Mine in Platinum, a hiker will appear and tell you the legend of the Alpha Pokemon and Sinnoh. He will continue to tell you the legend on the third floor of the Canalave Library. When traded to the upcoming HeartGold and SoulSilver games, your Arceus will create for you either a level 1 Dialga, Palkia, or Giratina when taken to the Shinto Ruins (jump to 2:30 for the cool part).