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. It is widely acknowledged as the main antagonist of the game.

Appearance
The Ender Dragon is a large, black dragon with purple eyes and four big, black legs with three toes on each one. It is by far the largest mob in the game, about 20 times as long as a pig, and is made of 61 cuboids, more than any other model. It has a few light gray features, such as the wings and various other parts of its body. It uses the dragon model Notch created, but utilizes a texture more reminiscent of an enderman, being black and scaly with purple eyes.

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. However, it does not emit particles like endermen.

Behavior
The Ender Dragon will destroy any blocks it comes into contact with, except obsidian, end stone, bedrock, command blocks and barriers. Instead of destroying them, the Ender Dragon passes through them. When hit, an Ender Dragon makes roaring, growling and snarling noises. The flapping of its wings can also be heard as the dragon moves. Unlike endermen, Ender Dragons don't take damage from water, nor do they teleport.

The Ender Dragon has a purple health bar that 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 healed by nearby Ender Crystals. Destroying an Ender Crystal while the Ender Dragon is being healed 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.

The Ender Dragon attacks by periodically charging toward the player. This charge can be interrupted by hitting the dragon with arrows. If the player is heavily armored, the dragon will not cause tremendous damage directly. However, the dragon can fling the player very far into the air, sometimes to fatal heights or even off of the map entirely. Therefore, although you can damage the dragon with a sword, the safest way to fight is with bow and arrows.

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. Entering the portal will activate a text cutscene that lasts for an average of 8 minutes, 30 seconds. After the cutscene, the player will be teleported to their spawn point/bed in the Overworld. The cutscene can be skipped by pressing the key (B on Xbox and O on PlayStation.) The player may return to the End after defeating the Ender Dragon, however there will be no new dragon.

When spawned in the Overworld using, the Ender Dragon exhibits the same behavior when killed, however, the End Portal spawned leads to the End, where another Ender Dragon still resides, and no text cutscene plays. Also, it seems to orbit around the origin (0 x 0) when not attacking a player.

The Ender Dragon will only target the player, however it can accidentally attack an enderman causing it to turn hostile towards the Ender Dragon, chase after it, and attempt to attack it, akin to when it is attacked by a player.

The ender dragon takes $1/4$ normal damage + 1 when hit in any part except the head. Therefore eggs, snowballs, and other attacks that normally deal no damage will deal damage to the ender dragon when not hitting it in the head.

Console Edition
In the Console Edition, the Ender Dragon's behavior is slightly different. While flying, the Ender Dragon fires Ender Charges, which cannot be deflected, at the player. After flying for approximately 30 seconds, the Ender Dragon will come down and hover over the unfinished bedrock portal, and remain there for another 30 seconds. The Ender Dragon will spew out "Ender acid", which deals damage, onto nearby players. Players may continually strike it with a weapon at this time. The Ender Dragon also fights endermen during this time, implying the reason for returning to the "nest" is to stop the growing clusters of endermen from stealing the egg.

Also, instead of the portal being spawned underneath the Ender Dragon's death, it is spawned in the middle of the island as soon as you enter the End. However, until the Ender Dragon is defeated, it will remain deactivated, and the Dragon Egg will not be on its podium. Until it has been killed, this is used by the Ender Dragon as a nest, where it will hover over it and attack the player with "Ender acid".

One final difference between the Console and PC versions is that some of the Obsidian Pillars have iron bars surrounding the crystal. This prevents the player from shooting it from a distance with a bow, ensuring the player has to climb some of the Pillars.

It is also aggravated in Creative mode and still shoots ender charges at you. Unlike survival, you cannot get killed.

Many of thes differences are planned to be implemented in the next update to the PC edition. (References are hard, please help.)

Video
Note: The video states the Ender Dragon is the only boss. This is outdated, as the video was made before the Wither was implemented.

Trivia

 * Name tags cannot be put on an Ender dragon.
 * In the Console Edition, Ender dragons cannot go through bedrock or obsidian.
 * Contrary to popular belief, the Ender dragon cannot be harmed by any mob other than a player or explosions. Therefore, the dragon will never purposely attack another mob, including a wither.
 * The Xbox avatar item 'Ender Dragon Pet' has the description 'A cuter, friendlier version of his bigger, less playful Minecraft sister.'- revealing that the Ender dragon is female. (Note: Quite a lot of people already knew this, noting that only females can lay eggs.)
 * 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.
 * 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.
 * The Ender Dragon's hitbox is larger than the Ender dragon itself, causing players to be pushed away from it.
 * The portal to the Overworld will appear at Y=64 at the X and Z location where the dragon died.
 * If you spawn the Ender dragon in a world and turn the difficulty to peaceful, the dragon will stay and not disappear, but will not be able to hurt the player.
 * If you kill a spawned Ender dragon in the overworld, it will create a portal to the real End, where there will be a separate Ender dragon.
 * Ender dragons can push other Ender dragons around.
 * Ender dragons will attempt to attack players in creative mode, though this has no effect.
 * When spawned in the overworld using the command, players in creative mode at a certain height force Ender Dragons to flap their wings wildly.

Notch-related trivia

 * 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?".
 * Dinnerbone later stated that he thinks the name is officially "Jean?"
 * 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."
 * 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.