Ender Dragon

The Ender Dragon is the first official boss mob to appear in Minecraft (with the second being the Wither). It only naturally spawns in The End. This mob uses the dragon model Notch created, but utilizes a texture more reminiscent of an Enderman, being black and scaly with purple eyes.

Appearance
The Ender Dragon is a large, black dragon with glowing purple eyes. It is the largest mob in the game. It has a few dark gray features, such as the wings and various other parts of its body. Similar to Endermen and Spiders, the Ender Dragon's eyes are visible through darkness, so you can see it coming from anywhere in the End.

Strategy
Before entering the End, it is very strongly advised that the player first sleep in a bed near the End Portal in case they die during the battle. It is strongly recommended that the player should have a full set of iron armor or higher, as any lower will get you easily knocked off The End by the Ender Dragon. Also have a diamond sword along with a bow and 2 to 4 stacks of arrows, or a bow with the Infinity enchantment, but note that the enchantments Fire Aspect and Flame do not work on the Ender Dragon. Also, TNT is not the best choice for defence/attacking the Ender dragon, because most of the time the dragon destroys the TNT before you have time to prime it.

Upon entering the End, a purple "Ender Dragon" bar appears at the top of the player's screen. This bar indicates the remaining health of the resident Ender Dragon. Each End dimension houses a single Ender Dragon whose health is periodically charged by nearby Ender Crystals. These crystals can be found at the top of Obsidian pillars that dot the landscape. As the healing effect of the Ender Crystals can reverse hard-won damage rather quickly, it is recommended that they be destroyed before the player engages the Ender Dragon.

Destroying an Ender Crystal while the Ender Dragon is being charged by it (indicated by a series of circles appearing between the Ender Crystal and the Ender Dragon) will cause the Ender Dragon to take additional damage instead of being healed. If the player repeats this method for all of the Ender Crysals, then the Ender Dragon will become weak and can be killed with no chance of it regaining health. Even after taking so much damage, it is still stronger than an average mob. Players can destroy an Ender Crystal either by meleeing it, or by hitting it with a projectile, including snowballs, etc. When destroyed, the Ender Crystal explodes, leaving behind a block of Bedrock.

Defeating the Ender Dragon in creative mode is quite easy, as the player can fly around and easily snipe or attack the dragon with melee attacks without having to worry about getting killed. But you MUST destroy the Ender Crystals as they will continue to heal the dragon even in creative mode. You have to worry about possibly getting knocked off the island because even in creative mode you can still die if you are knocked off the edge into the void.

The most common and easiest strategy to defeat the Ender Dragon is to destroy all of the Ender Crystals before attempting to fight the Ender Dragon, as any damage done to the dragon can be quickly undone by the crystals. Since Ender Crystals explode, an advisable strategy is to shoot arrows or to throw snowballs from a distance so the player does not take damage, then climb up the Obsidian towers with a ladder. This ensures that if the player falls off the tower due to exploding Ender Crystals, that player will be able to grab onto the ladder and not die.It is also recommended you wait until the Ender Dragon gets near to the Ender Crystals, then destroy it thus making it possibe for The Ender Dragon to take damage from the explosion. (However, it should be noted that the Ender Dragon can and will destroy the player's ladders).

If at all possible, the player should attempt to destroy the Ender Crystals while the Ender Dragon is too far away to detect or charge them. The player can wait for the Ender Dragon to fly near to the edge of the map, then run the other way until the boss's health bar disappears. The player can then safely destroy the Ender Crystals on that end of the map, taking care not to get close enough for the Boss's health bar to reappear. By repeating this strategy a few times, the player should be able to clear out the crystals from all parts of the map.

When the Ender Dragon charges the player, it is directly facing the player. This gives the player a good chance of attacking its head to deal extra damage. But if the player decides to attack it, he/she will have less time to try to avoid its attack. The Ender Dragon will also destroy any block it comes into contact with, except Obsidian, End Stone, and Bedrock. Instead of destroying them, the Ender Dragon passes through them. This makes TNT strategies difficult, if not impossible, to successfully execute. The Ender Dragon's swooping melee attacks have a significant amount of knockback if a player is hit by them, often knocking the player off of the platform in the End. The impact of the Ender Dragon's body and wings cause damage to the player, as well as knockback. A good way to prevent the dragon from knocking the player off the End platform is to make a 1-block hole in the End stone, in which the player then stands. The dragon will be unable to knock the player off, and can still be attacked. Occasionally, the dragon can knock the player just out of the hole. The highest armour and weapons, preferably all enchanted, are recommended. Because of the Ender Dragon's speed and flight, projectiles are favored over melee approaches. The Ender Dragon's immense health and evasive nature require a large ammunition stockpile. At least 2 full stacks of arrows are recommended since most will miss. Lava is useless, as it is immune to fire damage. Water is also useless, as it will take no damage from water and will destroy the block, however it can be used to make a "safe zone" which Endermen will teleport out of. Knockback enchantments are useless unless the enchantment is on grade 8 or higher (this is possible in SMP with modifications). Snowballs have the potential to stun-lock an Ender Dragon as its recovery time is slower than the firing rate of snowballs. Snowballs can also damage the Ender Dragon along with other thrown entities, such as Ender Pearls and Eggs. The Ender Dragon will take more damage from a melee attack than a ranged attack. Therefore, the player should wait for it to charge, sidestep, and then attack. Beds, which explode in the End, can be detonated when the Ender Dragon is nearby, causing considerable damage to it. This may be an exploit, but since exploding beds have been around since the End was created and have not been 'fixed' yet, it is more likely that it is a completely fair strategy and can be used if the player wishes to. Snow and iron golems are some what ineffective and rarely attack the dragon if at all. They end up wasting time in attempts to build them.

Another problem you may have while fighting the ender dragon is his Enderman minions. The high count of Endermen can be avoided in two simple ways. Its important to know that a Enderman will not become aggressive until you look directly at their upper body or head and can only be damaged by attacking the legs. The first way to avoid fighting the ender men is to not look at them with your cross hair. The second way is to equip a pumpkin in the head gear slot which covers up your cross hair allowing you to look where ever you want. This strategy's down fall is that it obstructs your vision making it hard to keep an eye on the dragon. The choice is yours whether to be carful were you look or to have low quality vision but not have to worry about where you look. The vision obstruction can be removed my switching to third person view but third person vision can also be difficult to use.

Invisibility will prevent aggression by Endermen. Since you have to remove your armor in order for invisibility to be effective, and the Ender Dragon itself ignores invisibility, this is a dangerous strategy.

Once killed, the Ender Dragon will appear to have beams of light spontaneously erupting from its body. It will then explode, dropping enough experience to bring a player from no experience to level 78 (12000 - 10 drops of 1000 experience, one drop of 2000 experience).

It will also spawn an exit portal with a Dragon Egg on top. (The egg is just a trophy, and will not hatch, but retrieving it can be non-trivial, see its wiki page for tips on how to do so.) Entering the portal will activate a text cutscene that lasts for an average of 8 minutes, 30 seconds. You can customise what this scene says in your minecraft.jar. After the cutscene, the player will be teleported to his/her spawn point in The Overworld. The cutscene can be skipped by pressing the key, and will instantly send the player to his/her spawn point/Bed in The Overworld. The player may return to the End after defeating the Ender Dragon, however there will be no new dragon. 

Ender Dragon in the Overworld or Nether
Using a modification, or the export-import feature of an external editor like MCEdit, it is possible to place one or multiple Ender Dragons into an Overworld or Nether map.

An Ender Dragon destroys almost any block it comes into contact with replacing the said block with air and displaying the white shock wave animation in the process. This makes it almost impossible to make a house in the end or when there is an Ender Dragon around the area of the structure. The only blocks not destroyed are those which occur naturally in the End: End Stone, Obsidian, and Bedrock. The Ender Dragon simply passes through these blocks without replacing them with air.

In the Overworld the Ender Dragon employs much the same attack strategy, flying and wheeling and recoiling if hit by arrows or snowballs. Generally the Dragon remains above the player, making holes in any hills it may encounter and when charging the player it can plough a track across the terrain launching any mobs or entities it may encounter into the air in much the same manner as when striking the player.

If the player retreats underground, the dragon continues to attack, mainly from above the horizontal plane the player is in, and in the process gouging large tunnels through the landscape and doing a lot of damage to the terrain.

In the Nether the effect is much the same, the Dragon carves tunnels through both netherrack and nether fortresses, and over time can carve out quite a large volume. If the Dragon flies through water or lava, like most other blocks, they are replaced by air and do no apparent damage to the Dragon. In essence, the Dragon can pass through the landscape with impunity.

If multiple Dragons are present, only one health bar shows in 1.2. The state of health seems to indicate that of the closest/last attacked Dragon, and if this Dragon is killed the bar reverts to another Dragon. If a Dragon's flight path takes it over the edge of the map, over unloaded chunks, it glitches and its animation becomes "stuck". If the player approaches the glitched Dragon, loading chunks beneath it, it resumes normal behavior. If the player tries to create distance between himself and the group of Dragons, generally one Dragon will do the majority of the attacking and the others will remain in the original area. Killing the attacking Dragon on a chunk that is far enough away from the others such that they are now over unloaded chunks will free the player from attack and clear the "Boss Health" bar from the screen. The portal created by killing a Dragon in the Overworld or Nether will lead to the End when used. If the player enters chunks on a large map where Ender Dragons have been placed with an editor, the "Boss Health" bar will appear, initially empty, but will fill as it "acquires" the nearest Dragon which will commence attacking in the normal manner.

If the player encases himself inside an obsidian or end stone structure (in Peaceful Setting), and allows multiple Dragons to repeatedly attack over the space of half an hour playing time or so, one or more of the Dragons can be observed to have changed their attack strategy, and repeatedly wheel and turn at close range and continually charge the player without much long distance flying between wheels and turns. A Dragon exhibiting this type of behavior can be rapidly killed with arrows.

It is advised that Ender Dragons should not be hacked onto any maps of value because of the damage they can cause.

Xbox 360 Edition
In the TU9 Update, the Ender Dragon spits out "Ender Acid". The Ender Acid is purple, much like the particles around the Enderman. They also fire a type of Acid Ball similar to Ghast, Blaze and Fire Charges, but with a more purple texture.

Video
''Note: The video states the Ender Dragon is the only boss. It was made before the Wither was implemented.''

History
Originally, dragons were a possible planned mob, hinted at by Notch during the Spider Jockey update. He also mentioned that dragon lairs may be an addition. They remained a potential work-in-progress until the Ender Dragon was announced.

Notch has stated in the past that if dragons are added, they will not be mountable as it would put too much pressure on SMP servers.

In September 2011, Notch stated that "dragons will be added eventually."

On October 7th 2011, Notch revealed the existence of the Ender Dragon.

On October 10th 2011, Notch released a video showing a small clip of the End that also shows the Ender Dragon fly into the top of the frame. 

On October 11th 2011 A player named stropping_notch asked Jeb if Dragon riding is an idea, to which he replied it is. It is not clear whether this means it is an idea under consideration or not, however, or whether it would apply to the Red Dragons or the Ender Dragon.

On October 12th 2011, in a Reddit post Notch also said, "They will be different dragons. The Ender Dragon will probably become larger, and the ones in the main world will be this size, won't go through terrain, and will be red because dragons are red."

On October 12th 2011, Notch stated in a twitter post that "Dragons have 6 limbs", consisting of 2 wings, and 4 legs.

On April 28th 2012, Jeb mentioned that he wouldn't be adding any more boss mobs until he makes the Ender Dragon "more fun first". Despite this, the Wither was added before any changes were made to the Ender Dragon. Therefore, we may be able to expect more boss mobs in Minecraft before the Ender Dragon is changed.

Bugs

 * If the game crashes while in the End, more Ender Dragons may spawn. This may also happen if Minecraft is closed during the Ender Dragon fight. This can cause problems with leaving the End and the player may have to slay multiple dragons to spawn a portal. Deleting and re-adding world from server will fix the issue.
 * Sometimes, the Ender Dragon will fly directly at the player without damaging the player, simply pushing them around.
 * If an Ender Dragon goes far enough from the player, it will stop moving, having a glitchy movement effect, however this is fixed upon getting closer to the Ender Dragon (Tested in SSP).
 * If an Ender Dragon is killed by an exploding ender crystal, it will die while being hit continuously by a healing beam with no source.
 * Rarely, once killed, there will be one and a half portals. (Tested in SMP)
 * Arrows fired at an Ender dragon from a dispenser do not deal damage to the Ender dragon but Arrows fired by the player do deal damage to the Ender dragon. The same glitch happens with snowballs and eggs. (Tested in SSP)
 * Very rarely, two Ender Dragons will spawn. (tested in SMP)
 * Logging out while the Ender Dragon is dying and then logging in again will cause the dragon to spin around randomly, failing to play its death animation. (Tested in SSP)
 * The gamerule, doMobGriefing will not stop the Ender Dragons destruction because the blocks around the dragon are replaced, instead of the dragon doing it itself (this bug was fixed in 13w11a.)
 * If you kill an Ender Dragon directly above an obsidian pillar with an Ender Crystal on it, the pillar will be destroyed, but the end crystal atop it will remain. (Tested in SMP)

Trivia

 * The Xbox avatar item 'Ender Dragon Pet' has the description 'A cuter, friendlier version of his bigger, less playful Minecraft sister.'- implying that the Ender Dragon is female, which is strange since gender doesn't exist in Minecraft.
 * The name "Ender Dragon" was first made known through a tweet by Notch reading "raqreqentba", which could be decoded using the ROT13 cypher, translating to "enderdragon".
 * On Reddit, Notch referred to the Ender Dragon as a she, and suggested her name to be "Jean?" in the same manner he called the Player "Steve?".
 * The Ender Dragon has its own separate mob folder containing separate designs: the old gray skin and the newer black skin.
 * The Ender Dragon flies at 10 times the player's normal walking speed.
 * Made of 61 cuboids, the polycount on the dragon is higher than all models in Minecraft.
 * Notch joked about how Minecraft was "going next gen" when deadmau5 mentioned this.
 * Before it was textured, Notch reported that he was afraid to texture it as it was a complicated model. In the end, the dragon model was so complex Notch stated that he gave up making the texture manually and wrote a texture packer tool to aid him in adding the texture to the model. Notch also uploaded the code for the tool so others could use the pack.
 * In terms of how difficult the Ender Dragon is to defeat, Notch tweeted that his design guideline for the dragon is " [If] I can beat it at all, it's too easy."
 * Due to the increase in Diamond Armor's durability since Minecraft 1.0.0, Ender Dragon attacks will barely faze the player. However, the launching aspect of their attacks can still subject the player to large amounts of fall damage, as well as possibly knocking the player off of the floating island and into the void.
 * Notch has uploaded a video showing why Ender Dragons will not spawn in the main world, as they would destroy any block they come into contact with.
 * On Reddit, Notch explained why Ender Dragons destroy matter.
 * When an Ender Dragon destroys a block by means of flying through it, an explosion effect occurs identical to that of a TNT explosion.
 * When hit, an Ender Dragon will makes roaring, growling and snarling noises due to the 1.4 update that adds brand new mob noises.
 * An Ender Dragon's attack can cause Endermen to chase after it and attempt to attack it to no avail, should they survive the devastating attack. This also works with blazes, wolves, and zombie pigmen (only works in creative due to spawn eggs being available to creative only).
 * Ender Dragons can be damaged by snowballs, as snow is made of water, which damages Ender-mobs. However, Snow Golems will not attack it.
 * Negative splash potions do not seem to affect the Ender Dragon. The potion hits and detonates as per normal, but the dragon does not flash red like when hurt and no apparent effect is seen on it. (Tested in SSP, and with Splash Potions of Poison, Instant Harming, Slowness and Weakness.)
 * The Ender Dragon's hitbox is larger than the Ender Dragon itself, causing players to be pushed away from it.
 * Even though Ender-mobs are injured by water, the Ender Dragon will destroy water source blocks as if they were solid.
 * The Ender dragon was the first mob which used wings to fly. The second was the Bat.
 * Firing large amounts of arrows at the Ender Dragon when it is above the 256 block map height limit will create a "flux", or large amounts of glitched arrows in a spherical pattern, that, when the Ender Dragon descends below the 256 block map height limit, will continually damage it until each arrow has been used. If there are any arrows left in the flux after the Ender Dragon dies, they will shoot out in all directions. If the arrows were launched using a mod item that causes arrows to home in on a target, then the arrows will find a new target to home in on, meaning that if you are in the End, then every Enderman there will start to attack you.
 * As long as the Ender Dragon is alive, the space texture of End Portals, as well as the player's view in the End, will have a slight multicolored static overlay to it.
 * If you go beyond the "island" in the End, the Ender Dragon will constantly attack you instead of circling around before striking.
 * If the Ender Dragon is killed when there is no solid ground below, the portal to the Overworld will appear approximately where the Ender Dragon died.
 * The Ender Dragon is immune to burns or any fire-related attacks from enchantments. It is also immune to cacti, poisons, and direct contact with water.
 * The Ender Dragon makes an appearance in the iOS title Dragon Fantasy alongside other mobs.
 * If you spawn the Ender Dragon in a world and turn the difficulty to peaceful, the Dragon will stay and not disappear.
 * The Ender Dragon will attack you even in Creative Mode.
 * The Ender Dragon can't destroy Minecarts with Chests, making them a good alternative to store your items while in the End. Just store them in an interdimensional Ender Chest. Keep plenty of spares.
 * Snow Golems and Iron Golems will not attack the Ender Dragon.
 * Despite being the last mob boss of the game, a Wither is drastically stronger, and when a Wither is built in the End, the Wither will easily kill the Ender Dragon due to its higher health (150 hearts), increased power (Withering does not damage the Ender Dragon, but direct Wither Skull hits still heal the Wither), and considerably stronger attacks (An Ender Dragon bash on Normal does 5 hearts. A Wither Skull direct hit can easily kill an unarmored player, hitting for 8 and 1/2 hearts and sapping 2 and 1/2 hearts' worth of Withering). However, if hacked or modded in, a wither will often search for other mobs instead of staying focused on the EnderDragon, often ending up in defeat.
 * The command will give the desired amount of mob eggs set to spawn an Ender Dragon, but nothing happens when the player attempts to use it, since this was a bug fixed in 1.2
 * If you set a Superflat world to the End biome (9), and go to 0,0 either by teleporting or moving there, the Ender Dragon will be there, and killing it will drop a portal to the real End. There will be a separate Ender Dragon in the real End.
 * Ender Dragon makes the same crackling sound as a firework when it dies.
 * If you are Invisible due to the effects of a potion, the Ender Dragon will see you and start to attack you. Also applies to Invisibility before and upon entering the End from the Overworld (Tested in SSP and in SMP, sees you both in first-time visits to the End, and every visit afterward).