In each “biome” there will be a specific area that is called ‘Guild Fortress’. These forts will be possible for guilds to take over. In these fortresses the guild can build different types of buildings such as auction houses, banks, crafting stations (ex. blacksmith), stables, local stores, storage houses, graveyards, etc.
Each fortress is unique, some are placed in the water, others upon a mountain and others are placed less strategically. There are different ways to attack each fortress.
When a guild takes over a Fortress in a certain area, they can make changes that affect the economy of that biome. The guild will be able to change the fee of the auction house, increase/lower the property tax of the apartments in the cities. The Guild master could be democratic and listen to the players or could also be a dictator who takes everything and does not pay any attention to the players. But the Guild master should be careful, so she/he does not get backstabbed from the guild mates.
To attack the fortress you need to be in a guild and you can do this at any time. To become the new overtaker of the fort, you need to destroy mostly everything. The guild that loses power of the fortress will lose everything that is within the fortress walls and the new Guild master takes over the ownership of the buildings/objects. The attackers can also build tools/weapons/vehicles/machines to make it easier to break down the fortress walls.
In order to defend the fort you need to have built walls around the fortress, you can also build defensive weapons to make the fortress stronger if an attack happens. It is also important to have players in your guild, so they can supply materials to make the fortress stronger and also help to defend it.
There are plenty of advantages to having a fortress. Your guild gets richer and you have the possibility to build storage houses in the fortress and this makes it easier for you to both farm and store materials. But there is a risk, if the storage house gets destroyed everything in the storage will be lost. Your Guild master could also impact the taxes (There is a cap on how much you can impact). Your Guild master could choose to get richer or share it with the guild, depending on how the Guild master shares the taxes. The guild will also be rewarded from the game since they are holding the fortress together.