When starting the game, you will notice darkened zones in the lower floors of your city. You can liberate these zones by completing quests. Liberating zones will grant you more building space, additional facilities, and base construction capabilities.
Sigils and Insignias
Collect Sigils and Insignias to expand into new zones. These items are typically collected from quest rewards. Different types are required for each floor, and you will have to progress through the quest line to collect new ones.
Monster Nests and Abandoned Mines
Nests and mines are home to deadly creatures that must be defeated first before expanding. The farther away the nest is from the castle, the more challenging your opponent becomes. Defeating the monsters inside will turn them into obstructions that will then need to be cleared.
Obstructions are structures that prevent you from creating facilities. Clearing these facilities will take time, and will yield some sort of reward. Obstructions like Withered Forests can be cleared immediately, but others like Monster Nests will need to be attacked first and turned into obstructions.