Mystcraft Ages

An Age is a self-contained dimension generated from the symbols written into a Descriptive Book. When a Descriptive Book is used for the first time, its Age is created; subsequent uses by the same or other players return to that same world.

Ages are described by combining symbols across several required and optional categories. A complete, well-formed Age generally specifies:

• A biome distribution (exactly one is required) plus the biomes to place into it.
• A world landscape / terrain type and the block(s) that make up the ground and any seas.
• A weather pattern (exactly one is required).
• A lighting mode (exactly one is required).
• Celestial bodies — at least one sun, one moon, and a starfield (each may be a normal or a "dark"/absent version).
• Optional visuals (sky, fog, cloud, water, foliage and grass colors, rainbows, etc.).
• Optional world features and structures and optional effects.

If a required element is missing, the grammar fills it in for the author, often by injecting additional symbols. Those injected symbols are a common source of unexpected results and instability, so experienced writers aim to satisfy as much of the grammar as possible up front.