Deoxys is a Pokémon that can switch among four different Formes. It's said that an aurora appears in the sky whenever it changes Formes. The Pokémon's stats change when it changes Formes, too.
Category: DNA Pokémon
Type: Psychic
Ability: Pressure
Height: 5'07"
Weight: 134.0 lbs.
Normal Forme
Deoxys has high Attack, Sp. Atk, and Speed while in Normal Forme
Attack Forme
In this form, it's Attack and Sp Atk are further increased while Defense and Sp Def are decreased by the same amount. Speed remains the same.
Defense Forme
Defense and Sp Def are greatly increased. Attack and Sp Attack are reduced to 46% while Speed is lowered to 60% compared to its Normal Forme
Speed Forme
All other stats are lowered at around 46-48% but the speed gets a great boost
Reference: pokemonrubysapphire.com