Castles are a vital part of the player's defence in Prime World. The castle is the first building the player will control, and the ultimate goal of a game is to destroy the enemy's castle and defend your own.
From the castle the player can build other buildings, such as barracks, citadels, mines and even magic gardens. The more buildings the player creates, the more units will be available to them, including Heroes.
- "Your impregnable castle is your realm's crown jewel. Mine resources to build new halls, improve your existing domain and construct a magnificent citadel, where heroes will be happy to live and proud to defend. Attracting different heroes means you must erect buildings which suit their needs and desires. Fairies will desire magical gardens to help them practice their magic. Swordsmen will be pleased to develop their fighting skills in military barracks. You'll be housing more than heroes in your castle. Taxes can be collected from peasant huts. Improve heroes' talents in the magic laboratory and obtain conjurer bonuses by building a library for ancient scrolls. You choose where these buildings are located in your dominion, creating the castle to your exact specifications. And since you’ll be tied into your social network, your friends are only a computer click away from seeing your spectacular estate and all its glory."