End Crystal

A series of floating crystals with pink cores, floating over fire on obsidian pillars in The End, were destroyed consecutively by the Fourth, Sixth, and War Doctors in a fight against a dragon. (NOTVALID: Doctor Who Comes to MINECRAFT!)

Behind the scenes
Although the crystals weren't named in Doctor Who Comes to MINECRAFT!, they were called 'End Crystals' in Minecraft. In Minecraft, the crystals heal the Ender Dragon, so most players will destroy them before attempting to actually defeat the dragon.