Biomes

Biome pages are modifiers. They modify a "biome controller" such as "Small Biomes" or "Single Biome", and can also be used by the feature "Floating Islands".

Like materials, biomes do not blend, but are pooled by the grammar until they are "picked up" by an appropriate primary symbol. "Single Biome Controller" will only take a single biome, and "Native Biome Controller" takes none, but the other biome controllers can absorb any number of prior biomes. Each Floating Islands symbol takes a single biome. As of V11, if biome symbols are left "dangling" at the end of the book (and a biome controller has already been specified), Floating Islands symbols will be supplied to absorb them.

All vanilla biomes are represented by symbols. So are any biomes supplied by other mods, unless the mod has taken steps to suppress their symbol. This means that some biome symbols may be available that represent work in progress, or which were not intended to appear as worldgen biomes. Using such biomes in an Age is fairly hazardous, ranging from unreasonable or dangerous contents for the Age, to actually crashing the game. A couple of examples from Thaumcraft: Its Eldritch biome generates as bare dirt, but spawns the advanced monsters found in Thaumcraft's Outer Lands (an endgame dimension). A more threatening example is currently found in the Thaumcraft add-on Thaumic Horizons: If its WIP "Pocket Plane" dimension is used in an Age, it will generate with a surface made of barrier blocks which don't render properly and do huge amounts of damage on contact.

The Nether's "Hell" biome does have a symbol; When used in an age, the area will spawn Nether mobs, but will not have the Nether's special prohibition on water, nor will beds be explosive. The End's "Sky" biome likewise has a symbol, but its page is restricted to creative mode for good reason: If coordinates (0,0) have Sky biome, an Ender Dragon can spawn.