Trade over the GTS as there are no more events for it
Pokemon to be exact dimond and pearl version on a ds
arceus if you can get one other than that i would say giritina
aftewr you get your national pokedex you will get a place where you can catch it only of you have the bayleaf on Ruby.
You get arceus by getting the black flute in Pokemon platinum or cheats for Pokemon dimond and pearl.Then go to Spear Pillar and you play the black flute.Then a stair will come and you go up and you will see arcues!
You can't except if you have an AC (action replay). After you get an AC, find the cheat code to get an arceus. I perfer the Pokemon modifyer.
It could be easy if you have a LV100 arceus shiny and when you beat all the elite in Pokemon dimond, pearl or platnium change arceus into fighting type and K.O. Cynthia.(only if you can)
get the azure flute then go to mt.cornet when you are there use it then special steps will appear go up them and soon you will get arceus. hope this helps
Dimond and Pearl Dimond and Pearl Dimond and Pearl Dimond and Pearl
arceus is the alpha Pokemon
arceus
arceus is an event pokemon.
the Pokemon # for arceus is 493