In the context of Mystcraft, an Age is a new dimension players can explore, similar to the Overworld, Nether or End in vanilla Minecraft. Unlike those dimensions, however, Ages have a wide range of possibilities. Players can find themselves in a Skylands age as pictured, or in an endless ocean with giant trees sprouting from the water. Advanced players can even write their own ages.
To travel to a new Age, players may Link by using a Descriptive Book either from a held book or a stand. The player will be transported to the Age with their inventory and experience, but the book will not travel with them. If the book was on a stand then it will remain there. If the book was in the player's inventory, it will fall to the ground, open. Books on stands can only take damage from rain and snow, while books on the ground will also take damage from water and anything that can hurt an entity such as a player. Books on the ground also take damage over time, so a covered book stand is the safest way to store a book.
Ages are generated based on the Symbols contained within the Descriptive Book used to link. When using a blank Descriptive Book, symbols will be automatically selected. If a player wants to customize their own age however, they can use a Writing Desk to copy symbols to and from their personal Notebook.
Players must be wary when traveling between ages: in order to get back to where they were before traveling to an age, the player will need a Linking Book created in the exact place they would like to return to. If a player forgets their Linking Book, they will usually be trapped with no way back to where they started. Their only hope is to find a Star Fissure to get back to the Overworld spawn.
Ages may also be unstable, leading to Decay. Decaying ages will fall apart around the player, eventually leading to a full collapse. Players must always be wary of shifting earth, as there is no other form of warning. Unstable ages are very difficult if not impossible to stabilize, though Skylands ages are more resilient to Decay.