Early in Disciples: Liberation, when you are still crawling through the sewers, you are introduced to the Frontline/Backline mechanic. Unfairly, the final battle of the sewers doesn’t give you the chance to learn about this mechanic on your own. Instead, you get to watch as the enemies get someone in the Backline.
The Frontline is something you have already gotten used to by now while using Avyanna and Orion. These units are your main force and are the ones that will be fighting for you in the battle. Your Leadership determines the number of units you can have on the Frontline. The figure increases as you gain levels, allowing you to have more units on the Frontline. The final total is 10.
The Backline is a more interesting part of the game. Each unit type has a special Backline ability that can only be used when units are placed in the back of the battlefield. Backline units can’t be attacked, but they can attack and offer support to your units on the Frontline.
For instance, Zombie units on the Backline inflict poison on whichever enemy has the lowest health while Possessed units grant physical might to allies for the duration of the battle. Having a combination of abilities works wonders when going into battle.
To add units to the Backline, you can wait for a battle and use the edit button to move your units around. You can also add units to the Backline by going to the units tab in the menu and editing them that way. Remember, you can only have three units on the Backline at any time, so it is good to mix and match abilities to see which ones you prefer.