Sevii Islands
The Sevii Islands (ナナシマ, Nanashima, lit. "seven islands") make up an area of the Pokémon world, introduced in the Pokémon FireRed and LeafGreen video games. The name would imply that there are seven islands in the Sevii Islands, but in fact there are nine islands in total, two of which (Navel Rock and Birth Island) are only accessible through special promotions, or by using a cheating device like Gameshark or Action Replay. Like the Kanto, Johto, Hoenn, and Sinnoh regions, the Sevii Islands are based on real-life locations, this time the Izu and Bonin Islands, south off the coast of Tokyo.
It is said that the islands were formed in seven days; this is the source of the name. An alternative form is 7 (SEV) plus 1 (I) and 1 (I) (the 1s being Navel Rock and Birth Island), thus forming SEVII. As well, it could be a portmanteau of Seven and VII (Roman numerals for seven). According to an old lady on Seven Island, however, these islands were named such because it was made in seven days.
On these islands, one can catch wild Johto Pokémon and four legendary Pokémon, all of which are not available in Pokémon Ruby and Sapphire.
Islands 1-3
These islands are accessible after the player defeats the seventh gym leader, Blaine. At that time, Bill will give the player a Tri-Pass at Cinnabar Island. The islands can be revisited by using the Tri-Pass in Vermillion City where the S.S. Anne was docked. No Johto Pokémon can be obtained from Islands 1-3 until the player has defeated the Elite Four.
One Island
One Island (Knot Island) is the biggest island. This island's Pokémon Center has a large machine that enables the player to trade with Pokémon Ruby, Sapphire, Emerald, Colosseum, and XD. To unlock trading, the player must retrieve two key items: the Ruby item and the Sapphire item. The player gives the items to Celio, a Pokémaniac and friend of Bill, inventor of the PC storage system. After the player has beaten the game once, he or she can obtain the two items, give them to Celio, and unlock trading between the games.
To the north is a place called Mount Ember. In FireRed and LeafGreen, the Legendary Pokémon Moltres has moved to this location. The Ruby item is also in Mount Ember.
Two Island
Two Island (Boon Island) is a small island. One house houses the Move Maniac, a person who can teach moves to the player’s Pokémon. Island Two is also home to a Game Corner, where players use the Game Boy Advance Wireless Adapter to play against their friends in two mini-games. ON the top of Cape Brink, an old lady in a house will teach the player's starter Pokémon a special move.
Three Island
Three Island (Kin Island) has a biker gang called the Kanto Rider Federation that the player needs to defeat. The player is searching for a lost girl named Lostelle on this island. After venturing into the forest, the player finds Lostelle under attack by Hypno. After saving the girl, the player can access the mini-games on Two Island. After Beating the Elite 4, you can capture Dunsparce.
Islands 4-7
These islands are accessible after defeating the Elite Four, getting the National Pokédex, and getting the Ruby from One Island. Celio will give the player a Rainbow Pass.
Four Island
Four Island has a day-care center and Icefall Cave. This day-care center can hold two Pokémon at once, allowing the player to breed for Pokémon eggs. Icefall Cave is a frozen cave to the east. In FireRed and LeafGreen, the player finds Lorelei attempting to stop Team Rocket. The player can help her out.
Five Island (Chrono Island)
Five Island (Chrono Island) is very large. This island is home to the Team Rocket Warehouse. The hero obtains the Sapphire item here which is vital for compatibility with Ruby and Sapphire, after the scientist snatched it on Six Island. South of the Warehouse is a memorial pillar for a boy's dead Onix. Five Island has a sea route known as Water Labyrinth in which Hoppip can be found. In this area, the player can receive an egg which hatches into Togepi. East of the Water Labyrinth there is an expensive resort called "Resort Gorgeous".
East of Resort Gorgeous, there is a cave known as the Lost Cave (reminiscent of The Legend of Zelda’s Lost Woods) a maze where Murkrow appear in Pokémon FireRed and Misdreavus appear in Pokémon LeafGreen. At the bottom of this cave is a lost girl named Selphy from Resort Gorgeous. She reacts with hostility and engages the player. Once defeated, the player is transported back to Resort Gorgeous, where she will ask to see a random Pokemon. If presented, she will give the player a random item which can be sold, or a Luxury Ball. If the player returns to the room in the cave where Selphy was afterwards, a Silk Scarf can be obtained there.
This island also is host to the Rocket Headquarters, where the handful of remaining Rocket members reside. They are surprised to learn that the player has defeated Giovanni and that the Team Rocket syndicate has been disbanded.
Six Island (Fortune Island)
Six Island (Fortune Island) is another large island. It has a forest called Pattern Bush, which has lots of Pokémon trainers and the location of Heracross, Ledyba and Spinarak. There are ruins to the south, which contain Yanma, Natu, Wobbuffet and Sentret. There is a mysterious building which has Braille encrypted that says cut to get in where the Sapphire is found but the Sapphire is stolen by a Team Rocket scientist. There is also Altering Cave, which shifts catchable Pokémon depending on the Mystery Events. Originally, only Zubat can be found in this cave. Mystery Gift can cause Shuckle, Aipom, Mareep, Stantler, Teddiursa, Houndour, Pineco, and Smeargle to appear, which are all exclusive to this area (except in Emerald, in which these Pokémon are encountered in the new area of Safari Zone)
In the games, the player must go out to a location called Dotted Hole to retrieve a sapphire.
Seven Island (Quest Island)
Seven Island (Quest Island) is one of the major islands. To the north is the Trainer Tower, which is similar to the Battle Tower in Ruby and Sapphire.
In the Trainer Tower you have to battle all the people to be able to get a prize at the end. There are four different typs of battles which are Single, Double, Knockout, and Mixed. Every time you beat all the trainers in one floor you can heal your Pokemon at the first floor before even proceeding to the next floor with fainted or injured Pokemon.
To the south, the Island contains Sevault Canyon, a location with high-level Pokemon and trainers. Further on down is Tanoby Ruins, where wild Unown reside. The player must first complete a puzzle in the Tanoby Key for the Unown to appear.
There is also a house in the main town that looks plain enough, but inside there is a stack of boxes blocking a doorway. It is unknown what is behind this doorway.
Islands 8-9
These two islands are only accessible thorugh special events. The player must have gone to a Nintendo event, or they can alternatively use a cheating device such as a Gameshark or Action Replay. These islands are also accessible in Emerald.
Eight Island (Navel Rock)
Players need the Mystic Ticket to enter this island. Navel Rock has only one cave, inside of which there are two Legendary Pokémon: Level 70 Ho-Oh and Lugia. Ho-Oh is found on the left side, while Lugia is on the right side.
If one uses an Action Replay (the one made for pokemon games only) the only game that can use the cheat is the UK version of Firered version. If you try to use it on the US version, there will only be one box on your computer, the name will be corrupted, and every pokemon in the box is an egg named 'bad egg'. This will also happen if you try to go to Birth Island on the US version.
Nine Island (Birth Island)
Players need the Aurora Ticket to access this island. Birth Island is shaped like a triangle, and on it there is a smaller triangle which the player can move around. After solving this triangle, a Deoxys (Level 30) appears. It will have an attack stat increased for FireRed, defensive stat increased for LeafGreen, and a speed stat increased for Emerald. Deoxys will change form depending which game it is in.