Enderman Robot Add-on

We've all heard the idea of robots replacing humanity, but it looks like the Endermen were the first ones to be replaced by the machine overlords (also known as the Enderman Robots). As it's a quite common spawn it's not really considered a boss, but it is most certainly more dangerous than most of the naturally spawning monsters. If you're looking for a new challenge in your world, then perhaps defeating an Enderman Robot could be it.