oke this villager is called the miner. he can only be fond in caves like bats and he walks around in the cave.
trading: you can trade items with him like coal, iron ore, iron ingots, gold ore, gold ingots, redstone, lapis and diamonds for mining tools like pickaxe and swords(enchanted or not).
enemys: well everyone but he can defend himself with a sword but it does less damage then the swords the player uses. so he can die but mobs will have a harder time.
appearance: he looks like a normal villager but he has (what looks like) iron armor on and a helmet that construction workers have.