I'm pretty wasted right now, but if I recall they're basically going into like.. a shadow-realm and reliving historical events and trying to manipulate them to have the best outcome to make sure humanity isn't weak when demons come or something. Skim a couple of the early/mid chapters for a refresher.
Basically, the shadow worlds are very game-like in scope, if not in mechanics. Basically, the Shadow World itself has very specific quest-lines that the participants must find and accomplish to succeed.
However, they are generally based on doing things in the opposite as history told. In this example... the tribe-people were able to succeed in their invasion and steal a bunch of food, leaving that estate and the city around it in poverty, causing the deaths of hundreds, if not thousands. In this Shadow World? They are meant to turn it around and ensure the invasion fails while leaving the two factions as tentative allies, even if not friends.
At least... this is what I'm getting so far.
@kronix its an artificial Shadow world made by the magic academy to train people, with similar objectives to the real ones. Its all about their worlds history, and knowing the motivations and persons and who did what and why.
I assume in the real ones there will be no quest markers though. Also the rewards are good, according to MC.
@Maala This one isn't training though. This is the real deal. Training ones just got skimmed a bit, plus the tower one I guess.
But this is definitely the real deal, they've talked before about how Desir wants the specific loot from this shadow world that'd help with his mana pool and such, and how he didn't personally go to this one in his original life, because again, it's the real deal and only the top groups were allowed in.
So the only thing they need to resolve now is the food crisis? That seems more difficult than the invasion. Especially since they had to give away food supplies to secure the truce.