A new priest class.
You can unlock new special 1 active slot for a priest class in your battle roster (bound to priest quest line). Then you can hire priest in the temple. Priests have different perks then common battle brothers, new class brings new interactions between battle brothers. Priest can use only blunt weapons and cant use metalic armor. Noble armies now can have priests.
Priest first ability Life energy can heal substantial portion of a comrade health in the battle or damage undead warrior. However, it needs a small blood sacrifice from a healer everytime it is used.
Priest 2nd ability Sacred incantation can break morale of an undead soldier and turn him to flee if priest resolve is high enough, can also be used against greenskin/beast to calm it from a frenzy morale. It can also be cast on an ally to one time increase of damage and accuracy. Incantation costs fatique.
Priest 3rd ability Magical fog puts 4 adjacent squares in to the misty fog which greatly increase ranged defense in those squares for 5 rounds. Fog also prevents reanimation of the (un)dead in that area, orc stunning jump / knockback and necrosavant darkflight. Can be cast only once per battle.