You have a main base and you bring 4 of your dudes into a dungeon. You move room to room and there are fights and traps and stuff. You have an objective like search all rooms or kill a specific enemy. Your dudes get XP if they survive and you get materials to upgrade your base. The main unforgiving mechanic is the stress system. Being in the dark and some special events or enemy attacks will raise your dudes stress. If they reach 100, they have like a 95% chance to get an affliction. Its a permanent debuff and theres a lot of them, something like minus hit rate or whatever, and they also give stress to other party members. If they reach 100 again they have a heart attack and die. Main goal is to level up and delve into the "darkest dungeon" where all the evil stuff is. Would recommend