Mines of Morgoth has a typical minimal plot for this type of game: killing the big bad guy at the bottom of the randomly generated dungeons underneath a village level with shops and a castle.
The game is mainly about exploring the underground and levelling up allowing more spells and better weapons, some magical, some not. Large number of combinations give quite a bit of depth and replay possibilities. Some of the environment is destructible but requires a digging tool. Some items are cursed and most need identifying to discover their true value. The catch is that this is only possible in a shop when selling said item or using an identify scroll. As these scrolls are limited, choices must be made and risks must be taken using unknown items.