I think you can get it when you have completed the completed the contests in resort area
Pokemon Diamond, Pearl, and Platinum have Arceus.
a
Arceus
I think arceus is the the strongest Pokemon in diamond and pearl. Also no moves are supereffective on Spiritomb and arceus
arceus
you get arceus at spear piller
Arceus is not possible to find in Pokemon Ruby. It was released in 2007 with Pokemon Diamond and Pearl
Ds action replay.
arceus i believe
Technically,yes you can get Arceus in Pokemon Heartgold,but only by trading it to your Pokemon Heartgold game from Pokemon diamond,pearl or platinum.
In the legend of Pearl, Diamond and Platinum, it is indeed said that Arceus is the creator Pokemon, therefore he created Time and Space, and Pokemon.
You Need The Arceus From 9th Movie or from Pokemon pearl/d/p