For the King is probably best described as a roguelite tabletop RPG. You form a party of three custom characters from a pool of different class archetypes and then go out into the overworld to do fights and complete quests until you reach the big bad. There's some time pressure because bosses called scourges spawn every now and then to create negative world effects if you don't kill them quickly enough, and each scenario has a very bad periodic effect that can only be canceled by progressing the main story. There's a lot of luck, but you can mitigate it by spending focus points or using equipment that boosts the relevant stat, and you usually get something out of even bad rolls. All of this works in co-op, too.
The base game has four different quests you can do, but now there's a fifth adventure that released as a paid DLC. It's mostly built around a vaguely Aztec civilization in the jungle that's trying to complete some kind of ritual to take over the world. You'd never come to this game for the story, though, so the large numbers of new enemies and new weapons are much more important. You can create some very unique builds more easily than in previous campaigns.
Still, the biggest difference between Lost Civilization and previous campaigns is that most of the main quests are gauntlet fights against several rounds of enemies with no breaks in between instead of dungeons with occasional stops in fighting for a trap or rest point. These fights can be very tight affairs, but it's extremely satisfying to get through them by the skin of your teeth. The overworld is also fairly light on the dungeon sidequests that were primary sources of XP in other campaigns, so you have to be braver about taking on tough single enemies and going in to fights above your level.
Lost Civilization isn't going to change your mind if you didn't already like this game, but as someone who did, I think this is my favorite campaign so far. It hones in on the tough combat and fun customization that have always been For the King's main strengths without getting bogged down in long overworld treks, and it has some of the most interesting aesthetics in the game. Highly recommended if you're looking for more content.
Time to beat: 9 hours
Platform: PC, also on everything