Battle Moveset

A Good Moveset for Deoxys would have to be this:

Attacks:

Extreme Speed Superpower Shadow Ball Rock Slide / Thunder / Ice Beam

Items Attached:

Choice Band

Preferred Nature:

Lonely or Naughty.

Strategy Using Deoxys

The Choice Band set is pretty much the standard for the Fire Red Deoxys. Due to having practically non-existent defensive stats Attack Deoxys is entirely reliant on hit-and-run, even attacks it resists can OHKO it. To compensate Attack Deoxys has a huge attack stat, quite capable of 1KOing many opponents, especially with the added boost from Choice Band. In general the set follows the standard rules of Choice Banders. Nothing resists both Superpower and Shadow Ball so one or the other will be able to give a strong hit to most opponents. With Extreme Speed Attack Deoxys can take out most things that outrun it (things that have boosts, Ninjask, Electrode and other Deoxys). Since there's a lot of Flying Pokémon in Ubers Rock Slide does well, Thunder can work alongside or against a Kyogre and Ice Beam can catch Groudon for a 2KO as well as hitting most fliers. Unlike with other Choice Banders Attack Deoxys has to be handled with delicate care, it has no immunities and can't take hits at all. It needs to be brought in by prediction or through a sacrifice. If you can predict one of your opponent's switches you can switch in as they make a switch, or you can switch it in after losing a Pokémon or possibly through a Substitute Baton Pass.

EV Corner:

EVs: 252 Atk / 252 Spd / 4 SAtk
Lonely Nature (+Atk, -Def) / Naughty Nature (+Atk, -SDef)

Pretty much the only way to go with Deoxys. It's possible to run a +Speed nature with Deoxys though, giving it enough of a boost to outrun Exeggutor, although with the +Attack nature it can still do bucket-loads of damage with Extreme Speed (although in most cases it won't grab the KO). The advantage of a +Speed nature is it has a shot at KOing other Attack Deoxyss.

Other Optional Sets

Attack Deoxys @ Petaya Berry / Lum Berry
Trait: Pressure
EVs: 4 Atk / 252 Spd / 252 SAtk
Modest Nature (+SAtk, -Atk) / Mild Nature (+SAtk, -Def)
- Ice Beam - Thunderbolt / Thunder
- Substitute
- Calm Mind / Shadow Ball / Superpower / Fire Punch

The special sweeper variation of Attack Deoxys. Since most people switch out against Attack Deoxys on a guess that it's a Choice Bander you can throw up a Substitute. After that you have the option to boost with a Calm Mind or go on the offensive, depending on the set you've picked. Between Ice Beam and Thunder/bolt you have a large amount of Ubers covered and with a boost from Calm Mind few can stand up to it's staggering Special Attack stat. Shadow Ball and Superpower serve as counters against special walls, Shadow Ball handles Defense Deoxys, Mewtwo and a couple of others while Superpower handles any of the non-Uber sponges like Snorlax and Blissey, since Defense Deoxys is more likely Shadow Ball will probably serve better. Fire Punch is just an additional option, it benefits from Sunny Day but that's pretty much all it's worth.

Other Optional Moves

Pursuit, Psychic, Psycho Boost, Solarbeam. With a combination of four different potential Deoxys forms, as well as having an Uber move pool, Attack Deoxys ends up with a huge load of options, although for the most part it can't capitalise on those options on account of it's crappy defence. That pretty much leaves it with the offensive moves that haven't been put into any of the two core sets. Since a lot of Pokémon switch out against Deoxys Pursuit does well for catching running opponents. Psychic and Psycho Boost gain STAB but in Ubers there's a lot of Pokémon running around who are Psychic types, and the ones who aren't usually have a weakness to Ice Beam or Thunder/bolt, rendering it pretty much useless. Solarbeam is a strong grass attack that works well with Sunny Day but there's always a risk of a Kyogre or Tyranitar switching in to ruin the fun.

Strategy Against Deoxys

Against the Choice Band variation of Attack Deoxys there's only a handful of Pokémon who can stand up against it without taking a lot of damage. Groudon can handle most of it's physical moves but is 2KOed by Ice Beam. Defense Deoxys can take most of it moves except for Shadow Ball. A lot of Pokémon with priority moves (Quick Attack, Fake Out and Extreme Speed) can KO Attack Deoxys but most Attack Deoxys users are smart enough to switch when faced with those threats. The best way to take out Deoxys is to out-predict the Deoxys user, catching Deoxys with a reasonably strong hit can cause a KO. With the support of a speed boost a fair few Pokémon can outrun Deoxys but still need to be aware of a potential Extreme Speed. Against the Special Sweeper variation a handful of Pokémon can wall it depending on the moves it carries. If it doesn't have Shadow Ball Defense Deoxys can stand up to it and if it doesn't have Superpower Snorlax and Blissey and with Superpower and Fire Punch absent Registeel and Regice can handle it as well. As with the Choice Band variation it's just as fragile and quite easy to KO when caught by surprise. Unlike the Choice Band variation it's quite likely to lack Extreme Speed so Pokémon with adequate speed boosts usually don't need to worry against it.

Contest Moveset

A good Contest Moveset for Deoxys would have to be this for the Smart Contest best with Calm, Gentle, Careful, Sassy Nature:

Attacks:

Calm Mind
Psychic
Reflect
Psycho Boost

Items Attached:

Green Scarf

Strategy Using Attack Form Deoxys

If you do the attacks in this following order you should have very few problems; 1st - Calm mind, 2nd - Psychic, 3rd - Reflect, 4th - Psycho boost, 5th - Psychic

Locations in Games

Ruby/Sapphire/Emerald Not In R/S Colosseum Not In Colosseum Fire Red/Leaf Green Island 9 on Fire Red ONLY

Animé Appearences

Deoxys has had a couple of Anime Appearances. First, one crash landed near LaRousse City and started hunting for its partner. Going into the Attack Form in order to do the most damag against is adversaries, it eventually left. After that, another Deoxys Crashlanded in Kanto and started going a bit mad until it was qwelled by a Pokémon Ranger Movie 7: Visitor Of The Space Fissure! Episode 448: Pokémon Ranger! Deoxys Crisis!