ORAS remakes Hoenn with Gen 6 mechanics, and the roster plays completely differently from the original Ruby and Sapphire. Fairy type exists now, Mega Evolution adds power spikes, and Primal Reversion turns Groudon and Kyogre into 770 BST monsters. DexNav lets you find hidden abilities in the wild. Same Hoenn region, radically different power levels.
Showing all 723 Pokemon that can exist in Omegaruby Alphasapphire, including transfers from other games.
How to access additional Pokemon in Omega Ruby & Alpha Sapphire
DexNav changes everything about wild encounters in ORAS. Sneak up on rustling grass and you'll find Pokemon with egg moves, Hidden Abilities, and boosted IVs that normal encounters don't have. It's the best wild hunting tool the series has ever added.
After the story, soaring on Latios or Latias opens Mirage Spots where legendaries from every past region appear. The Delta Episode hands you Deoxys. Between those and Bank transfers, all 721 are obtainable.
Nidoking
Clefairy
Clefable
Paras
Parasect
Venonat
Venomoth
Diglett
Dugtrio
Meowth
Persian
Mankey
Primeape
Growlithe
Arcanine
Poliwag
Poliwhirl
Poliwrath
Bellsprout
Weepinbell
Victreebel
Ponyta
Rapidash
Slowpoke
Slowbro
Farfetch'd
Seel
Dewgong
Shellder
Cloyster
Gastly
Haunter
Gengar
Onix
Drowzee
Hypno
Krabby
Kingler
Exeggcute
Exeggutor
Cubone
Marowak
Hitmonlee
Hitmonchan
Lickitung
Chansey
Tangela
Kangaskhan
721 total, same as X and Y. The Hoenn regional dex is expanded over the Gen 3 originals. Fairy type exists, Mega Evolutions are available, and DexNav lets you find Pokemon with hidden abilities and egg moves in the wild.
Gen 6 mechanics: Fairy type, Mega Evolution, Primal Reversion, and DexNav wild encounters. Primal Groudon and Primal Kyogre hit 770 BST. The Delta Episode postgame adds Rayquaza and Deoxys. And you can fly on Mega Latios/Latias in the Soar feature.
Primal Reversion is like Mega Evolution but exclusive to Groudon and Kyogre. When holding the Red Orb or Blue Orb, they revert to their primal forms automatically upon entering battle. 770 BST each with upgraded abilities: Desolate Land (Groudon) blocks Water moves, Primordial Sea (Kyogre) blocks Fire moves.
Mudkip is still the best. Mega Swampert gets Swift Swim in rain and 150 Attack. One Grass weakness, dual STAB Earthquake plus Waterfall. Blaziken with Speed Boost is the competitive pick, but Swampert is more reliable for the story.
Generation 6, released in 2014 for the Nintendo 3DS. They're remakes of Gen 3's Ruby and Sapphire using the X and Y engine. Same Hoenn region with Fairy type, Mega Evolution, and updated graphics.
DexNav is a tool on the bottom screen that shows which Pokemon you've caught in each area and lets you hunt for rare ones. When a Pokemon is "detected," you can sneak up on it. The detected Pokemon may have hidden abilities, egg moves, or higher-than-normal levels. It's a unique catch mechanic that no other game has replicated.
- Gen IY
Yellow151 Pokemon - Gen IRB

Red & Blue151 Pokemon - Gen IIGS

Gold & Silver251 Pokemon - Gen IIC
Crystal251 Pokemon - Gen IIIRS

Ruby & Sapphire202 Pokemon - Gen IIIFRLG

FireRed & LeafGreen151 Pokemon - Gen IIIE
Emerald202 Pokemon - Gen IVPt
Platinum210 Pokemon - Gen IVHGSS

HeartGold & SoulSilver256 Pokemon - Gen IVDP

Diamond & Pearl151 Pokemon - Gen VBW

Black & White156 Pokemon - Gen VB2W2

Black 2 & White 2301 Pokemon - Gen VIXY

X & Y457 Pokemon - Gen VIORAS

Omega Ruby & Alpha Sapphire211 Pokemon - Gen VIIUSUM

Ultra Sun & Ultra Moon403 Pokemon - Gen VIISM

Sun & Moon302 Pokemon - Gen VIILGPE

Let's Go Pikachu & Eevee153 Pokemon - Gen VIIISwSh

Sword & Shield400 Pokemon - Gen VIIIPLA
Legends: Arceus242 Pokemon - Gen VIIIBDSP

Brilliant Diamond & Shining Pearl151 Pokemon - Gen IXSV

Scarlet & Violet400 Pokemon - Gen IXLZA
Legends: Z-A364 Pokemon - Gen XWW

Winds & Waves51 Pokemon