The Heart of Evil DLC adds a new type of world to the game with opposing fortresses.

The player arrives on the scene just when the fortress that is being defended by a garrison of NPC dwarves has almost fallen. Most of its defenders have been killed or captured by the forces of the dark fortress for unknown experiments.

DLC details:

• A new campaign level designed for experienced players;
  
• Two fortresses, between which there are continuous skirmishes, raids, and battles;
  
• Periodic reinforcements for the defenders of the fortress will help you restore your defenses and turn the tide of this great battle;
  
• There are also new monsters, items, structures, and building blocks.