What are the Sevii Islands?

The Sevii Islands are an archipelago south of Kanto, created for FireRed and LeafGreen and reachable by ferry from Vermilion City. Players count nine islands in the chain, seven of them bearing the numbered names the archipelago is known by, One Island through Seven Island, with Navel Rock and Birth Island standing apart as event destinations.

The first three islands open during the story, but the archipelago's real role is post-game. After the Elite Four, a quest for Celio, the islands' network administrator, sends the player across the chain after two gems, the Ruby and the Sapphire, and completing it opens trading with Ruby, Sapphire and Emerald, stitching the remakes into their own generation.

The islands hold the remakes' strangest corners: the Tanoby Ruins on Seven Island, where every form of Unown waits in seven chambers, the Altering Cave, the Trainer Tower, and a Rocket warehouse that continues the first game's story rather than merely repeating it.

They are the clearest statement of the remakes' philosophy: preserve Kanto exactly, and build the new material offshore, where 1996's map ends.