The reverse side of each Island Board shows an alternate map. These maps represent the canonical Spirit Island, and prioritize theme more highly than the front “balanced” sides: land types cluster together, wet terrains tend to be on the windward side of mountains, etc.
The Thematic Boards are intended for experienced players, both because finding terrains at a glance is harder with the more realistic art style, and because some of the changes make the game more difficult: more lands per board, clustered terrains, more starting Invaders, etc.
THEMATIC BOARD SETUP
The Thematic Boards have a fixed layout relative to each other. You can use any of them that you want - but for the definitive geography at each player count:
Some lands overlap slightly onto other boards. A land is always considered to be on the board where its land number and Setup icons are. Ignore any unattached land fragments; they aren’t in play.
Some lands have Setup icons for tokens from the Branch & Claw expansion; ignore them when playing with just the core game. Illustrations of Spirits, rivers, and wildfires are for flavor and do not alter gameplay.