An Enderman (inspired by the Creepypasta character Slender Man) is presumed to be one of the most creepiest mobs in Minecraft. They are sometimes considered peaceful but are actually extremely frightening. Endermen will steal any blocks or mushrooms, flowers, etc.
Appearance
Endermen are completely black, with purple 3x across pixeled eyes. They are 3 blocks high making it one of the tallest mobs in the game (alongside Ghasts, Slimes, Magma Cubes, and others) When the Enderman is non-hostile they have purple "flower" or "dust" like substance that appears when it is around. But when it becomes hostile, its mouth opens (which they have 2 teeth, and inside its mouth its see-through) and black smoke comes out followed by the purple substance. Endermen have long limbs and legs related to that of an iron golem and skeleton.
An angry Enderman holding a grass block.
Combat
Again, Endermen are neutral, which means they will not attack unless the player attacks them, however, When the player looks with the crosshair directly into the Enderman's face or eyes (either one) it will become hostile, but before it attacks, it will stare upon you from a distance. When it attacks, it dashes extremely fast at you(similar to teleporting). When it touches you, you take damage (4-10 hearts depending on difficulty, potion effects, enchantments and armor strength). Endermen's weakness is water, when it touches it it will automatically teleport away and become passive again, but still takes damage. This is a good way to deal with an Enderman chasing you about. To kill an enderman with a stone, or wooden sword, it takes about 5-6 hits. With a iron sword, it takes 5 hits. With a diamond or golden sword it takes up to 4 hits, (enchanted) will take about 3.
Spawn
Endermen do not have a Spawner. They spawn on both dimensions, the Overworld, and the End. They will spawn on caves or where ever there is shade. When it is on the day time it rarely attacks, only on caves or dark areas. Endermen will teleport to a farther place on the day, if you go directly foward to it. Endermen are rare to spot, but not as rare as a Spider Jockey or Iron Golem. Endermen will not burn on sunlight, because they aren't joined on the undead. On the End they often spawn, since they are the only mob (not including the Ender Dragon) that lives or populates in that dimension.
Drops
Endermen are one of the Mobs that gives more XP than usual. They would drop 5 XP, and would drop Ender Pearls. When they drop Ender Pearls only about 2 would be spotted.