Enderman

The Enderman is a mob that was introduced in the Beta 1.8 version beta; part one of 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 (like zombies and skeletons). Their exact size is 0.6x0.6x2.9.

As of Minecraft version beta 1.9 pre release 4, Notch has created End Dimension, their homeworld, where they spawn frequently. Due to the name of the dimension being the End, and Endermen simply having it as a prefix, it is believed that the Endermen originated in the End.

Preventing Attacks
As Endermen are 3 blocks tall, you can keep your house 2 blocks tall to prevent Endermen from teleporting into it, if you happen to look at one. However, if you build a tower that happens to be the size or shorter than a hill next to you, the Enderman can still teleport into your castle or home. If you aren't in your house and you look at one, though, you have to keep your crosshairs on it until you're close enough to kill it. Also, if the player sits in a pool of water, the Enderman will take damage from the water and then teleport away in response to the damage, and then run back to the player in an attempt to attack. They will usually repeat this mishap until getting killed. If the player wears a pumpkin on their head, an Enderman will not turn hostile when looked at. They cannot teleport to you when they are in minecarts. They will not teleport to you if you are on a sufficiently high tower. Lastly, if the player simply does not aim the crosshair on an Enderman, it won't attack.

Killing Endermen
Despite their somewhat unsettling appearance, Endermen are damaged by water, fire, lava, rain and attacks. 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, stone, and gold swords may not deal enough damage to kill the Enderman before it kills you. Cacti will also damage Endermen, so a wall of cacti also serves as a passive defense against Endermen.

As of the 1.9 Pre-release 4 If you use water to kill an Endermen in The End it will simply just disappear. It is unconfirmed if this is a bug or intentional.

Hostile Endermen will teleport away when the player closes in on them to strike. When this happens in a small underground space, the Enderman may 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. The player can also change to 3rd person view by pressing F5 to make sure he or she can't be attacked from behind because of the Enderman tendency of teleporting behind them. Most of the time Endermen will pick up a block once it engages pursuit against a player.

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

As of the 1.9 Pre-release 2, Endermen teleport to avoid being hit by arrows and splash potions and teleport to a new location when hit with one. They are no longer damaged by sunlight in this version, and when they touch water they immediately teleport away. Thus, when it is raining, one can sometimes see a curious sight - a "red" enderman rapidly teleporting randomly across the landscape.

An efficient way of killing an Enderman is by attacking its legs constantly with a sword or an axe.

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). They will not give you the blocks when you kill them.

In 1.8 Pre-releases, Endermen were able to pick up any block, including Bedrock.

The source code of Mob Endermen in Beta 1.8 indicates they will only pick up blocks of the following types: After 1.8, Notch announced that he would be changing the way in which Endermen interact with blocks. As of Beta 1.9 Pre-release 2, Endermen are now limited to the following blocks:

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

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. This is most noticeable in wooded areas where Endermen are important forestry pests as they damage 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. However, this is not impenetrable, since they can still teleport inside when provoked by the player or even randomly by touching some water.

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)

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

Future
Notch had stated "Endermen suck because they're annoying, and because I nerfed them and made them too easy. I shall fix this." In 1.9pre3, Endermen have 20 hearts of health, requiring 4 hits from a diamond sword to kill. They instantly teleport away upon contact with arrows, water, sunlight and splash potions of harming, but not potions of poison.

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.
 * In SMP, Endermen don't open their mouths or shake when aggressive.
 * 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. This can also be avoided by making the enderman_eyes.png translucent, even only slight translucency will fix this.
 * If an Enderman is holding a block and the world is exited and then re-entered, the data 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. This is due to a mixup in the saving/loading of Endermen entities, it is saved as carryingData and tries to load carriedData.
 * If a hostile Enderman is forced to teleport because they have wandered into a water block they will no longer be hostile to the player, it is yet unknown if this is a bug or not.
 * If a hostile Enderman is attacked by another mob and kills the attacker, it resets to being neutral towards the player.
 * In the Minecraft Beta 1.9 Pre-Release 2, Endermen commonly teleport away from the player, even if they were just attacking him/her, and become neutral.
 * If an Enderman picks up a flaming block (i.e. Wood, Netherrack, etc.) and then places it again, the block will be extinguished, but the Enderman will be on fire.
 * During the day in 1.9 pre-release 5, if you look at an Enderman, it will open its mouth and become hostile but if you try to shoot a projectile at it, it will teleport and become neutral. Also if you look at it without shooting it, it will open its mouth, shake, and become hostile then when you look away, it will become neutral again. Only happens during the day.
 * If you look at it, it will only stay hostile if it can run toward you; if it has to teleport to get to you, it will become neutral. Only happens during the day.
 * The Enderman will randomly teleport during the day. On small islands it will start teleporting in a spastic manner.
 * On rare occasions, if the player and an Enderman are on opposite sides of a large body of water and the Enderman turns hostile, it will stare back at the player like normal but will never attempt to get closer, even if the player is not staring back. It will continue staring at the player for a while until it suddenly disappears.

Trivia

 * At first when Notch designed the Enderman he thought it was not 'creepy' enough, coming with the idea that having a situation which the player would want to avoid could make the Enderman significantly more scary. This gave Notch the idea to implement the staring feature where aiming the reticle on the Enderman's face would cause a suspense in which breaking eyecontact would trigger an attack, as well as the Enderman having the ability to teleport so that when the player has stared at the Enderman they will have to face a consequence for that action.
 * 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 widely regarded as 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.
 * Because many found the name "Enderman" unappealing, they had petitioned to change the name "Endermen" to "Far Landers", as if to imply that their natural habitat was the Far Lands. Notch had stated, however, that he would not change their name, regardless of this petition, going as far as to joke that he should instead change the name of the Far Lands to "The End", sneakily foreshadowing the addition of the End dimension where the Endermen live.
 * 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.
 * In version 1.8, Endermen sound like zombies, but that is a place holder; new sounds were made, but not yet implemented. In the prerelease of version 1.9, Endermen are completely silent. This is only until 1.0 (1.10), when the new resources will be downloaded.
 * 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.
 * 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 white 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.
 * Endermen do spawn in the rain.
 * The reason Endermen are damaged by the rain and by water is because Burnie Burns, founder of Rooster Teeth Productions, and his nine-year-old son Jack were visiting Mojang as part of a project. Jack saw Notch running from some Endermen in the rain and suggested that they take damage from water as a vulnerability.
 * In the 1.8 Pre-release as well as the 1.8 Pre-release 2, Endermen originally had green eyes and emitted black smoke. In the full release of beta 1.8, the eyes were changed to purple and black smoke has been replaced with purple particles similar to the particles emitted from Nether portals.
 * Like every other creature in the game with the exception of Spiders, Endermen can't see the player through transparent blocks such as Glass.
 * In the 1.9 Pre-release 2 Endermen will teleport away whenever they are damaged by anything other than a direct player hit, including sunlight, cacti, other mobs, arrows, and water.
 * Endermen can harvest cacti and collapse the entire cactus. However, they are known to replenish the numbers of cacti in the desert by planting their cactus blocks, and since they generally don't take the bottom block, the harvested cactus generally regrows during the day.
 * Endermen can teleport very far, even when moving several hundred kilometers from them, they will continue to follow until killed.
 * If an Enderman carrying a block is killed, that block is not dropped on death.
 * In the 1.9 Prerelease it is possible for an Enderman to create a snow golem.
 * An Enderman cannot be aggravated by a snow golem, as they cannot be hit with projectiles.
 * Only up to 30 Endermen will follow you.
 * An effective way to gain easy experience is to go The End Dimension, make a 1x1 tower 4 high, stand on top of it, look at Endermen and have them teleport to you while you slaughter them. They cannot reach you because the tower is too tall. However, without any conventional methods of being able to leave the end, it would be pointless unless you enchant in the end.
 * As of 1.9 prerelease 4, Endermen won't burn in daylight, but instead they will teleport away when the player walks up to them in the daytime, making it impossible to get close enough to kill them.
 * Even in an aggressive state, they can still pick up blocks.
 * Before Beta 1.8 pre-release 1, Endermen were originally planned to have dog-like ears.
 * In 1.9 pre-release, if you were to pour water on a hostile Enderman, the Enderman will teleport away and become neutral again.
 * When an enderman picks up a flower, the flower will appear to be floating between their grasp.
 * In 1.9 pre-release v.4, if you look at an Enderman the inventory bar will be highlighted.
 * Since they burn in sunlight, like skeletons and zombies, but, are not able to cool those flames down by jumping in the water, since that also hurts them, the only way you could find an Enderman during the day is if he is in a secured dark area.