Dungeon of the Endless

In principle, a fairly simple achievement. Just try to always keep the heroes together, if you see that the hero is not coping, take him out of the room where the battle is taking place. Never open doors to more than one room at a time - this may cause a huge pile of monsters to come out of the darkness. Also, watch what you put on your heroes. Some items force monsters to attack a specific hero - you should not equip such items on weak heroes. And, of course, always have an emergency supply of food for treatment.