you cant.
Only from a trade or special event.
You can't catch it, but you can trade for one from Pokemon Diamond, Pearl, or Platinum.
If you are looking for Arcues you need to trade it with either Diamond or Pearl Version.
you catch unowns just to fill out your unown notes. nothing happens when you catch all 28 of them including ! and ?
Arcues is a event Pokemon but it is in the hall of orgin only obtainable by having a havens pipe.
You Can't
nowhere
You cant get an arceus in soulsilver or heartgold at all!
You can't get Arcues on Emerald. It didn't exist back then.
Yes
arcues
Arcues Any of them it depends how you train them.
you have to get it from Pokemon platinum or diamond