The Homebase Storm Shield, or simply Storm Shield, is the setting for the mission type Storm Shield Defense. In the tutorial, you build a generic fort around the Storm Shield Generator. As the game progresses, you can build whatever type of fort that you want.
When the Storm Shield expands, the actual shield itself becomes unable to keep the Husks out. During this time, you must protect the Storm Shield Generator from being damaged by Husks. You will either receive a amount of time during which you must protect your fort, or a certain amount of enemies to kill. There are usually 4 waves, 1 or 2 in the beginning defenses.