After reaching Yllian, you learn how to edit the land and build new structures. Unfortunately, you don’t have any new structures to add. That is where the phasing mechanic comes in. You can use this mechanic to destroy buildings and build them again later for a cheaper cost.
To phase out a building, you simply need to select the building in Yllian you want to get rid of. The option to phase out the building will appear in the building’s menu alongside the recruit units and train units options. Selecting the phase-out option will make a warning display that states you can always rebuild the structure later.
Once a building is phased out, you will see that it is phased out whenever you go to build a new building in a vacant area. The cost to rebuild the building will initially be 500 Gold, and that price will gradually increase each time you phase the building out and rebuild it. The price increases by 500 Gold each time you rebuild it.
If you decide you want to phase out a building that has been upgraded, you can always rebuild it later. It will retain all the upgrades it previously had before removing it. Upgraded buildings cost the same to rebuild as standard buildings, and the rebuild cost gradually increases each time you rebuild it.