Enderman

The Enderman is a mob that was introduced in version 1.8; The Adventure Update. The Endermen are 3 block high, black creatures with long arms and legs, glowing purple eyes and a purple particle effect similar to a Portal. They are rare in comparison to other mobs (with the exception of the spawner-only Cave Spider), but can still be seen regularly at night on the overworld in groups of up to five. Their two iconic abilities are the ability to pick up and move blocks and teleportation. Endermen take damage from coming in contact with water (including water blocks and rain) and sunlight. Their exact size is 0.6x0.6x2.9.

Behaviour
Endermen spawn as neutral mobs and will normally mind their own business, wandering aimlessly like other mobs and occasionally picking up blocks, carrying them for a time and then randomly placing them on the ground elsewhere. However, if a player looks at them by placing his or her crosshair directly over them for half a second, they freeze, stare back at the player, open their mouth and become hostile. The Enderman can detect unwanted scrutiny from a range of 64 meters - four times the search range of most other aggressive mobs.

After becoming agressive, they will stay frozen as long as the player doesn't move the mouse. When the player moves the mouse, even if only by one pixel and in any case regardless of whether it's still pointing at the Enderman, it will quickly run at high speed towards the player. If they are a long distance away, the Enderman will teleport, roughly halving the distance to the player with each teleport until within it is within 16 meters. Once within range, the Enderman can teleport to avoid melee attacks and will often manifest behind the player.

Preventing Attacks
It is important to note that the Endermen will become aggressive if players attack them. It is safe to look at them through transparent blocks like glass, glass panes, iron bars, ice and vines - but not stacked half slabs.

Endermen will not attack players who are wearing a pumpkin while looking at them.

It should also be noted, that looking at an Enderman's legs or head will not stop them from attacking. The player must look at the torso to prevent further attacks.

Further, an Enderman in a minecart seems to be incapable of attacking.

Killing Endermen
Despite their appearance, Endermen are easier to kill than most other mobs, since they are damaged by water, sunlight, fire, lava, rain and attacks alike. Emptying a bucket of water on the ground will damage the Enderman without it becoming hostile to you. Arrows and all types of swords are effective against one, though wood and stone swords may not deal enough damage to kill the Enderman before it kills you.

Hostile Endermen will teleport away when the player closes in on them to strike. When this happens in a small underground space, the Enderman will teleport into inaccessible caves or to the surface. They will not teleport back to the player unless he/she moves to an area that has enough space for the Enderman to teleport back. On the surface, an Enderman's tendency to teleport away when the player is close enough to attack can be used to keep an attacking Enderman at bay.

When killed, regardless of the method of death, any blocks held by the Enderman disappear. They do not drop or get placed.

Moving blocks
Endermen will pick up and move both natural and player-placed blocks. They will pick up blocks horizontally nearby within a short reaching distance similar to the player's, at heights from their feet to their head (3 layers).

The source code of MobEndermen indicates they will only pick up blocks of the following types: As of Beta 1.9 Pre-release, Endermen are limited to the following blocks: Player testing has indicated that they cannot pick up the following blocks:

Boats, minecarts, and mobs are entities and cannot be picked up by Endermen.

Notch has announced that he will soon be changing the way in which Endermen interact with blocks.

In 1.8 pre-releases, Endermen were able to pick up any block, including bedrock.

Damage to Structures and Environment
Because Endermen possess the ability to move blocks, they can cause damage to the natural environment and player built structures. For players with access to significant resources, Endermen may not represent a real threat in combat but are considered nuisance household pests. At present, Endermen are able to move player-placed blocks and the resulting holes can let in other mobs in addition to being simply unsightly. Fortunately, their manipulation appears to be random and as such, simply increasing the thickness of exterior walls (increasing the number of blocks Endermen must move from the same location to compromise security) will greatly reduce the chance of a catastrophic failure before it can be repaired. In some circumstances, removing a single block can have profound consequences on a structure due to what the block is holding or holding back. An Enderman may, for example, elect to remove the glass cover from a lava light or a block supporting torches, redstone wiring, switches, or a door. Such critical components should be made structurally redundant, fail-safe, and kept out of reach of Endermen.

On the overworld, signs of Endermen activity will soon start to become apparent in frequently loaded chunks, recalling the legends of Herobrine. This is most noticeable in wooded areas where Endermen are important forestry pests as they damages trees by removing parts of the trunk near the ground. They will also take leaf blocks and place them on the ground where, much like player-placed leaves, they will not decay. In desert areas, Endermen pollinate cacti by removing blocks and placing them on fresh sand, gradually increasing the population of cactus in frequently loaded deserts. They will also cause damage to structures in NPC villages, causing fire and flood if their curiosity takes them to the smithy or irrigation embankments.

A common Enderman defense is to place lava or water moats around well-lit structures.

Notably the Endermen can reach through blocks to grab blocks behind so put anything important two blocks in, or make walls multiple blocks deep.

A common misconception is that vines prevent Endermen from taking blocks, however Endermen will not pick up vines and will reach through them instead (like stairs)

Enderman do not spawn in lit areas, but they may wander into lit areas from adjacent dark ones, so simply lighting structures liberally with torches is not a guaranteed defense.

Bugs

 * In SMP, Endermen do not charge if you look at them. However, their vision bounding box is off, so if you look above the Endermen, they will become aggressive.
 * If an Enderman picks up a block with a tile entity, such as a chest, its contents will be deleted.
 * When using a custom texture pack, Endermen will be bright white overlapping their texture. This is caused by the blank spaces of their enderman_eyes.png file. If you create a custom texture pack you must make sure that you only change the 6 pixels actually used by their eyes. An alternative would be to use the original png from the minecraft.jar in your pack. Using the most recent release of MCPatcher also fixes this bug.
 * Endermen do not appear to be as rare as they were originally intended to be. They can often be seen in groups of up to 5.
 * When your crosshair is on the Enderman, and it is still frozen, you can hit it from an extended distance than normal reach.
 * If an Enderman is holding a block and the world is exited and then re-entered, the damage value of the block is not preserved, and will reset to 0x0. For example, in the case of the wool, it will become white wool, and brown mushroom blocks will display the pores texture on each side.

Trivia

 * If a Skeleton shoots an Enderman when attempting to shoot the player the Enderman will completely stop chasing the player even after it has killed the offending Skeleton.
 * The name "Enderman" is a reference to the Internet meme known as "the Slender Man", a similar-looking fictional cryptid. The name was given to the mob by Notch in a Reddit thread.
 * Due to the similarities to the Slender Man, many have petitioned to change the name "Endermen" to "Far Landers". Notch has stated however that he will not change their name, regardless of this petition, going as far as to joke that he should change the name of the Far Lands to "The End" instead.
 * At the PAX Beta 1.8 demo, Endermen dropped diamonds; in the actual release they have a chance to drop an Ender Pearl.
 * Endermen have the ability to open their mouths. In their texture, their jaw is separated from their skull and in the 1.8 Official Trailer, an Enderman attacked the camera with its mouth open. This makes the Enderman the first mob with the ability to physically open their mouths without switching to a different texture. They only open their mouths when they attack. Due to the player's perspective, the player sees the back of the Enderman's head when they open their mouths. If a player is one block higher, they see through the Enderman's open mouth. They open their mouths by moving their skulls higher than their jaw.
 * As of now, Endermen sound like zombies, but that is a place holder; new sounds were made, but not yet implemented.
 * Endermen's eyes glow in the dark, like spiders'.
 * Endermen's full body glows in the fog. (Like Spiders)
 * Endermen seem to shake while you look at them.
 * When you pause the game, the Enderman will keep shaking.
 * What Notch wrote in his first official description of the Endermen, "-the feeling of control", may have meant more than it appeared, referencing a deeper fear in players, the fear that they now had something closer to an equal, and thus something to challenge their control.
 * Endermen seem to have a smiley face pattern on the back of their heads.
 * Contrary to popular belief, there are no other eye colors besides purple. The mob/enderman_eyes.png file in minecraft.jar only has one color, and what looks like what eyes in mob/enderman.png is actually the spot where the eye texture gets overlaid, to make the eyes glow like spiders'.
 * When an Enderman picks up a block, it makes the sound of that block type being destroyed.
 * Endermen are quite common above ground, as stated above, spawning in groups of sometimes about 5, while below ground they are a bit rarer and cannot spawn in low roofed areas, such as confined caves. It is not recommended to run underground to get away from them as they may still spawn and will chase you if provoked.
 * The color of Enderman's eyes went through a few changes. In the first preview, Endermen had white eyes. In the 1.8 pre-release, Enderman had glowing green eyes instead of purple.
 * Endermen do spawn while it rains.
 * The reason Endermen are damaged by the rain and by water is because Burnie Burns, founder of Rooster Teeth Productions, and his son were visiting Mojang as part of a project. Jack saw Notch running from some Endermen and suggested that they take damage from water as a vulnerability.
 * Despite his slender appearance, Enderman is capable of lifting a 19.3 ton gold block.