End Crystal

The Ender Crystal is an entity found in The End. They are found on top of the many Obsidian Pillars found across the End, and their primary purpose is to recharge the health of Enderdragons. When attacked, they explode, leaving a block of Bedrock in their place. The base appears to be made of Bedrock, with a crystal hovering over it and fire in engulfing it. The player must destroy a majority of these in the immediate area in order to defeat the Enderdragon effectively. If the Enderdragon is regenerating from a crystal when it is destroyed, then the Enderdragon will take about as much damage as if you had hit it with a diamond sword.

Strategy
The recommended method of destroying one of these entities is to shoot one with an arrow, although snowballs and eggs also work. The player may climb on top and attempt to destroy one by hand, but the resulting explosion might not only hurt the player, but throw them off the tower. Note that during this, the player will be in danger of Endermen attack, and even worse than that, the Enderdragon coming. Another way to reach the top of the towers is to throw a Ender Pearl up to the top, also these aren't exactly rare in the end. If the player wishes to destroy one by hand, it is advised to mine the Obsidian around the tower, instead of creating ladder or stairs out of material that might be broken by the Enderdragon.

Trivia

 * Enderdragons may be damaged by the explosion given off when one is destroyed, provided they are close enough to it.
 * When created naturally, they are layered directly over a Bedrock Block, which is most noticeable when viewing one from below. The player will see glitching of the textures where the two overlap.
 * Placing water above one using a Bucket will cause a looping effect, whereas the fire is continuously put out and reinitialized as the water attempts to flow down and is stopped. The water will not spread, as it can flow downward, but is being prevented by the reoccurring fire instantly taking its place.
 * Even when blocking the healing beam by a wall, the healing beam will go through the wall.