Goblins

Goblins would act like underground villagers. You can trade ores with them to get stuff like pickaxe and sulfur cave locator maps(sulfur caves, lush caves and mineshafts should have locator maps). They also mine ores like farmers(but instead of harvesting crops, they would mine ores). If you attack them, they will start attacking you. Hostile mobs don't attack goblins. You can breed goblins with rotten flesh.