What Dungeons 4 is about
You play as the Absolute Evil, working alongside your loyal servant Thalya to push back the forces of good. The core loop is split in two: underground, you dig out and furnish a dungeon that suits your creatures' needs, and above ground, you send those creatures into the Overworld to take it over. Digging out rooms and corridors is only half the job, since the Overworld fights back. Dwarves have moved in underground to claim resources, and Dwarves, Elves and Humans all send raiding parties after your dungeon's heart, so traps and defenders matter as much as expansion.
Evilness is the resource you gather to flip the Overworld to your side. Beating Mini Bosses like the obsessively harmonious Unicorn earns you Evilness, which you then spread across the land to turn lush forests and plains into evil biomes. Thalya has an ability-based Perk system that unlocks new powers as you go, and the customizable Evil Hand lets you govern your creatures and slap subordinates. Your army draws from the Horde, the Undead and the Demons, with Snots playing a much more prominent role than before.
Playing it together
Dungeons 4 supports 2-player online co-op, and both players manage a single dungeon together rather than running separate ones. Every map from skirmish mode and from the campaign can be played cooperatively, so you can work through the whole story with a friend or pick a skirmish map when you just want a session. Splitting the work is the natural way to play it: one of you digging and building rooms while the other pushes out into the Overworld, or both of you coordinating on where to spend Evilness and how to defend against incoming raiding parties.
Before you start
The campaign is narrated by the English Narrator from the previous titles and runs alongside several skirmish maps, so there is a story path and a shorter-session path. Dungeons are up to four times larger than in the previous game and hold more creatures than before, which means your plans can get sprawling quickly. Expect resistance in both directions: your dungeon needs traps and defenders against raiders hunting your heart, while your armies need to hold ground in the Overworld as you convert it. There is also a Level Editor available if you want to build your own maps.