An Underground Civilisation

Potetntially there could be a new mob similar to the villager such as a gnome, or elve. It could make for a different trading method for more ores and use a different kind of currency, say for instance gold! It could add more lore to the mineshafts as maybe they could have unabandoned Mineshafts near their villages. It would be a nice surprise to be strip-mining and suddenly coming across one of these and add a new level of epicness to the game.