Pokémon FireRed Deluxe: Champion — the postgame
What opens up at this point in the game, and everything you can catch by now that you couldn't before.
✓ Four Island onwards: the rest of the Sevii Islands, the Rocket Warehouse, the Johto gym leaders waiting at Canyon Entrance and Sevault Canyon, Cerulean Cave, the Crystaleye Cavern, and the last few fights in the game.
Newly reachable
Crystaleye CavernFour IslandIcefall Cave EntranceFrozen ChamberIcefall Cave 1FIcefall Cave B1FIcefall Back CaveFive IslandWater LabyrinthResort GorgeousLost CaveFive Island MeadowMemorial PillarWater PathRuin ValleyDotted HoleGreen PathOutcast IslandPattern BushSeven IslandCanyon EntranceSevault CanyonTanoby KeyTanoby RuinsTanoby ChambersTrainer TowerNavel RockBirth IslandCerulean Cave 1FCerulean Cave 2FCerulean Cave B1FCrystaleye Cavern 2nd Floor
Newly catchable (135)
Bosses around here
Trainer Gold (Four Island) — Lv 60Rocket Admin Ariana (Rocket Warehouse) — Lv 61Rocket Admin Archer (Rocket Warehouse) — Lv 62Trainer Silver (Rocket Warehouse) — Lv 63Falkner (Canyon Entrance) — Lv 61Bugsy (Canyon Entrance) — Lv 62Whitney (Canyon Entrance) — Lv 63Morty (Canyon Entrance) — Lv 64Chuck (Sevault Canyon) — Lv 65Jasmine (Sevault Canyon) — Lv 66Pryce (Sevault Canyon) — Lv 67Clair (Sevault Canyon) — Lv 68Developer BPark (Sevault Canyon) — Lv 69Trainer Kris (Monean Chamber) — Lv 70Champion Steven (Five Island) — Lv 70Developer SMBZ (Trainer Tower) (Double Battle) — Lv 70Professor Oak (Cerulean Cave) — Lv 85Pooper Derek (Crystaleye Cavern) — Lv 90Final Boss Dom (Seven Island) — Lv 100