Ender Dragon
From Craftland Minecraft Aether Server
The Enderdragon is a Vanilla boss mob in Minecraft. It has 100 health however, there are towers around its fighting area that heal it slowly as long as the dragon is still in range. When the dragon is killed it will drop a significant amount of experience, a couple of bottles o' enchanting, and a dragon egg. If you hit it once with the dark scythe the dragon will also drop a dragon soul.
Tips: -You can take out the towers easily with a Hammer of Notch