The Legion feature becomes available once your base reaches Iron Blood level 4 at minimum. After that, you can follow these steps:

-Go to the Officer's Camp and click on it, then select "Legion Camp."

-Click on "Select Officer."

-Choose your desired officer from the list.

-Select the desired base skin and drone (UAV).

-Once you have all the required items, such as the officer's s legion emblems and others, click "Create Legion."