You must trade from another game.
You can't.
You cannot catch Deoxys or Jerachi. They are obtained via a Pokemon event.
If I remember right, its Latios,Rayquaza,Deoxys,Jirachi, and Groudon.
the Unobtainable Pokemon in RSEFRLG are Celebi, Mew, Jirachi, Deoxys, and 000 (Missingno. ( DO NOT ATTEMPT TO CATCH))
You can catch Groudon,Rayquaza,Latios,Deoxys,Celebi,Jirachi,regiice,regirock,registeel,and Mew
Blooduh
I have no Idea about it on Ruby But I do know its on emerald. But My brother was talking about Deoxys on Ruby so Its a 50/50
you cant catch a deoxys in Pokemon soulsilver or heartgold but u cud trade it over from ruby Sapphire or emerald or use an action replay
You can't catch arceus, unless your doing a gameshark or hack. But you can catch deoxys, kyogre (in sapphire), groudon (in ruby) rayquaza and the three regis. Also, you can catch jirachi oh, I forgot, deoxys is an event too. i
you cant get deoxys in platinum dumbnuts only emerald ruby sapphire so be smarter dumbnut!!!!!!!!!!!!!!!!('_')
You can't catch Deoxys in the wild or a special place. But if you got it in Pokemon FireRed, LeafGreen, Sapphire, Ruby, or Emerald you can migrate Deoxys in the Pal Park in the Kanto region in Fuchsia City.You cannot obtain Deoxys legitimately in Pokémon SoulSilver. You must take advantage of an Event in Pokémon Emerald, FireRed, or LeafGreen to go to Birth Island using an Aurora Ticket, and catch it there, then use the Pal Park to transfer it to SoulSilver. Alternatively, you can cheat.
You need to migrate it from FireRed, LeafGreen, or Emerald. But if you have a Deoxys in Pokemon Ruby or Sapphire, then you can migrate from them to Pal Park.