You can't change it's form in the third gen games, it changes depending on the game - sapphire is normal form.
you touch one of the meteors in veilstone city with deoxys as your party leader
You can't really change it forms... but the only way to let it change forms is to trade it to other versions like leafgreen, firered and ruby or sapphire
You cannot find Deoxys in Pokemon HeartGold. Deoxys has to be traded from another game to get into HeartGold. The rocks to the east of Pewter City are used to change Deoxys' forms, but you have to transfer one using Pal Park, first.
Deoxys (Referenced As Pokemon #386 In The National Pokedex) changes forms via a variety of methods. In Ruby and Sapphire Deoxys will appear in Normal form, In LeafGreen it is shown in its defense form, FireRed shows the Pokemon in its Attack form and Emerald Shows it in its Speed form. Diamond, Pearl and Platiunum versions, Deoxys can be changed by increasing any of its Speed, Attack or Defense stats to change it to that specific type. To return it to normal type all stats need to be even/level. With HeartGold and SoulSilver Deoxys can be changed by coming into contact with certain meteorites in one of the main cities.
In Pokemon FireRed, LeafGreen, Ruby, Sapphire, and Emerald, you cannot change Deoxys' forme. Each game has its own forme and must be traded around to get the forme you'd want. In Pokemon Diamond, Pearl, and Platinum, there are meteorites in Veilstone City on the east-south of the city. Visit Nacrene City's museum in Pokemon Black(2) and White(2) and have Deoxys be in the first slot of the party and let it touch the meteorite to change forme. You can change its forme, also, in X and Y games. You will need to visit the museum in Ambrette Town and let Deoxys interact the meteorites. In Pokemon Omega Ruby and Alpha Sapphire, you can go to Professor Cozmo's house in Fallarbor Town and interact with the meteorites.
Just like any other pokemon, you battle with it. You can change its forms on the route East of Pewter City
you have to go to veilstone city and there are 4 forms of deoxys: speed def attack normal if you go to the metorite in the pits there have deoxys in your party and if you press a at it it will make deoxys cry and it will say it will increase the offense defrense or speed or it will say it blanced them out and it will become normal. PS if you no how to glitch or hack Pokemon Sapphire email me at cabeers55@AOL.com
There is one Pokemon with different forms: deoxys- speed, attack, normal, and defense.
You have to Migrate from Fire Red, Leaf Green or Emerald. Or you can use the Action Replay Modifier Code. Also by touching the Meteorites' at the South East of Veilstone City with Deoxys in your Party you can change Deoxys into 4 new forms. Below are the forms. Top Meteorite- Speed Deoxys Middle Meteorite- Change Back to Normal Deoxys Bottom left Meteorite- Attack Deoxys Bottom Right Meteorite- Defense Deoxys
Deoxys is a legendary Pokemon which has various different forms. To find one in FireRed version, you need to have an Aurora Ticket.
to use this sone you must have Deoxys then take it to the craters and have it touch one it will change forms, it will change into speed,defense,attack,or somthing else. - AcidBurn
You need Deoxys first of all. Use W.T.W to find the Form Transformers.