The Ender Dragon is an extradimensional being that inhabits "The End". She's the final boss of Minecraft, although after defeating her you can still continue the game. After death she drops a unique item called "Dragon Egg" and a lot of experience points. It is unknown if she is the only Ender Dragon.
Behavior
Unlike the humanoid Enderman that will only attack if attacked or stared at, the Dragon is aggressive and will attack players or anything that attacks it. The Ender Dragon is also an extremely territorial creature and treats whole The End dimension as her property.
Abilities
An Ender crystal.
As well as its natural ability of flying, the Ender Dragon can also regenerate herself by using Ender Crystals placed on high pillars made entirely of obsidian.
She also has the ability to shoot Dragon Fireballs which leave a lingering cloud of dragon breath behind, and she sometimes flies to the end exit portal to breathe out her deadly breath. In this state she's invulnerable to arrows.