Deoxys

Deoxys is a legendary Pokémon from the Pokémon series of games. It is a promotional, "secret" Pokémon obtainable only through special Nintendo promotions, much like Mew or Jirachi. It has incredibly high stats and is famous for its four different forms, depending on which third generation Pokémon game it's being used in.

Deoxys' name comes from deoxyribonucleic acid - DNA. The Deoxys movie Destiny Deoxys and its Pokédex entries say that Deoxys was actually a virus that arrived on Earth after the meteorite it was on crashed on Birth Island, which later mutated into a Pokémon after "exposure to a laser beam". The crystal on its chest is actually its brain, which is can shoot lasers from. It is extremely intelligent as well, and has psychokinetic powers. While his Speed form is configured for maximum agility and ease of movement, its Attack form can change its appearance to fool enemies. When in its Defense form, it changes its cellular structure in order to absorb attacks. All this information seems to confirm that Deoxys can control the structure of its own DNA, a reference to its connections to the virus and its ability to change the DNA/cellular functions of its host cell.

Deoxys' Forms
Depending on which game you're playing, Deoxys may have a "form" specific to that version, except Diamond, Pearl and Platinum, in which there are a few meteorites scattered around that allow Deoxys' form to be changed. Each form has different stats, and different learnable moves. However, once Deoxys learns a move in one form, it will know it in other forms as well. With effort, one could trade Deoxys around to obtain the best moveset for whatever form they chose to use it in.

Normal


Normal Deoxys is the Deoxys you'll be using if you're playing Pokémon Ruby and Sapphire. Its focus is on insanely high Attack, Sp. Attack and Speed, with terrible HP and defenses. It has little staying power, but can at least survive better than Deoxys-FR (Attack Deoxys). Still, most of the things Deoxys-F is good at, Deoxys can also do, but not as effectively.

Suggested Movesets
If you want to sweep Physically, slap on a Choice Band, a hold item which doubles its attack while forcing it only to use the move it chooses upon its first turn in battle. Extremespeed, Shadow Ball, and Superpower are excellent choices for that. If you want to special sweep, use Ice Beam, Thunder, Calm Mind and Substitute.

Attack


Much better. Attack Deoxys is found in Pokémon FireRed, and it's commonly referred to as Deoxys-FR or Deoxys-F thanks to it. While regular Deoxys can barely survive one hit, sometimes being able to squeak out being 2-hit KO'ed instead, Deoxys-F does exactly the same but with much higher speed and stronger attacks. With equally high Attack stats it can be physical, special, or mixed. It is the absolute best cleaner in the game if used properly and makes the most powerful Pokémon, period. An absolute monster that gets destroyed if something manages to survive a hit from it.

Suggested Movesets
See normal Deoxys. Really, this thing does everything it can do 100 times better. Anything with Extremespeed has a chance at taking it out, such as Rayquaza. Without Extremespeed though Deoxys-F has the potential to destroy whole teams. The Choice Banded version is the most common, with the filler commonly being a Fire/Ice move so that Steels and Dragons don't show up to spoil your fun. A special set could also work, but you'll get the most mileage out of Choice Band.

Defense


Defense Deoxys can be used in LeafGreen. A total wall. It takes every hit like it was nothing, and laughs as it Recovers whenever it wants. The problem, of course, is its low Attack and Sp. Attack and mediocre Speed - most fellow legendaries can outrun it easily. Toxic is a great choice for Deoxys-L. Just stall with Recover and let Toxic slowly eat away more and more at your opponent, sometimes earning you a free turn when they switch out. It's also probably the best tank and Spiker in the game.

Speed


The Deoxys seen in Pokémon Emerald, Speed Deoxys or Deoxys-E. Despite being far less one-dimensional as Deoxys-F or Deoxys-L, Speed Deoxys is used considerably less, but can still do a ton of things. Although its attack stats are average for a Legendary, its speed makes it an excellent user of Choice Band. This makes it an excellent "revenge killer" - your opponent takes out one of your Pokémon, and you send in Deoxys-E (who most likely will go first) to finish off the job with Shadow Ball, Superpower, etc.