End Crystal

An End Crystal is both an item (in 1.9) and an entity found in the End.

Natural generation
End crystals are found atop the many obsidian pillars in the End.

Naturally spawned
Their primary purpose is to recharge the health of the ender dragon, who will charge from the nearest crystal within a cuboid extending 32 blocks from the dragon in all directions. The dragon is healed each half-second. An ender crystal can heal multiple ender dragons at the same time. The healing beam is neither obstructed nor is its power diminished by entities or blocks.

When attacked, even by attacks that normally deal zero damage, they will explode. The ender crystal's explosion is the same power as a charged creeper, 50% more powerful than TNT. Any ender dragon charging from the crystal when it is destroyed will take damage.

The base appears to be made of bedrock, with a crystal hovering over it. While in the End a crystal will continually generate fire at its current position, one block above the base (directly on top of the block the base is embedded in), replacing any other block at that location. The end crystal entity is not solid and can be walked through freely. Ender dragons will pass through the crystal with impunity.

End crystals can be pushed by pistons, but if they are moved while in live fire they will catch fire and explode.

As items
As items in 1.9, end crystals may be placed on bedrock and obsidian, if the two blocks above the bedrock or obsidian block are air or replaceable blocks and no other entities intersect the area. If one is placed on each of the four sides of the end exit portal (the central bedrock block of each side or the ones adjacent to it), the crystals will respawn the healing crystals and the dragon before exploding.

Data values
Ender crystals have entity data which defines various properties of the entity. Their entity ID is.

Trivia

 * Placing water above an ender crystal using a bucket will cause a looping effect, where 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 prevented by the reoccurring fire instantly taking its place.
 * Since fire is only checked when an entity moves, ender crystals do not normally take damage from their own fire.
 * Oftentimes, the fire will stay after an ender crystal blows up.

Gallery
Enderkristall Cristal del Fin Cristal d'Ender Endkristal Kryształ Kresu Кристалл Края 末影水晶