You have the town area think of that as your hub. Quests , items , blacksmith for upgrades. everything you mine is kept on death. There is a guy you can sell your mined stuff too and he upgrades the castle which upgrades you , the stuff found in mines , etc that is also kept on death. the mine itself is randomly generated. There is green lights you will see this will help you last longer in the mine so the fog wont kill you. The fog is always going to be there i believe it is timed. when you reach the bottom that is as far as you can go. There is a chest down there with a rare item and you die and start all over. but with random stuff there is npcs you will find and quests and things. The more you upgrade the castle you also will encounter new enemies and story elements along the way. The jar is used to open a soul door if you are lucky enough to find it. The more souls in the jar the better loot you get. Fill the jar by killing stuff. hope that helps explain it! There are bugs but who cares the game is a blast and you keep your materials before the crash so its not big deal really.