You need an eon ticket, only available from Nintendo conventions. You also used to be able to send your game to Nintendo to get an eon ticket, however this no longer works.
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 can't.
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.
breed deoxys
Groudon, Kyogre, Rayquaza, Deoxys and Jirachi!
There are 202 including jirachi and deoxys.
Use this gameshark cheat code Deoxys 8C5DE8C8A33E9D88 or C5946A0E65BE02B0 or FBC061A9072FC320
you really can not get deoxys in Pokemon ruby but you could get a gameshark and hack and i think you need aurora ticket
In Pokemon Ruby there is the 3 regis, rayquaza, latios, groudon, deoxys, and jirachi. So there are 8 legendarys.
There is no spaceship on ruby it was a old rumour of a way to get deoxys and jirachi.
deoxys named Pokemon is only in Pokemon emerald, fire red and leaf green
You must trade from another game.