(After Light and War Update 26-Jul-2013): The Pure Element is no longer a wildcard in the Breeding System. It demoted to an ordinary Element. i.e., if you breed a rare Dragon with a rare dragon you will almost certainly get a Pure Hybrid (20 hours) or a Pure Dragon (10 hours). You may also (if you're lucky) obtain another Legend.
After the Light and War update Pure Dragons are not opposite to Legendary Dragons.
Unknown how, it's first attack is Lava Balls which is a Flame attack.This also makes its' breeding result possible to any flame dragon, like breeding it with Ice Dragon can result a Cool Fire.
As of the LaW update, Pure Elementals are now Pure Hybrids.
The Pure element was, originally, the only element to have no weaknesses against any element or deal strong damage against them. It was also dealt weak damage to Pure Element by itself each other. Now this element had been re-designated to pure attacks, which are critical damage against Legend Hybrids. Later, After Primal Element was introduced, Pure Element is now weak against Primal Hybrids.
Now you can place Pure Hybrids inside Elemental Habitats. For example, you can place Pure Terra inside Terra Habitat.
Elemental Crystals now boost Pure Hybrid earning. Pure Dragons do not enjoy this boost, because there are no Pure Crystals as of yet.
After the update, all Pure Elemental habitats replaced with normal Pure Habitats.
After the Light and War update, breeding two pure dragons or two Pure Hybrids can result in Legendary Dragons.
Pure dragon has the highest hatching time out of all the elemental dragons.
This dragon can learn Pure Light Attack only once, although the option shown twice. This makes the Pure the only Dragon that has only two Trainable Attacks.
Did you know -- SP originally had another name for the new Legend icon. They intended to release another new element named Eternal. For unknown reasons they changed their mind on this. The new design for the Pure Dragon is proof. This was originally intended for the Eternal Dragon.
Pure Dragon's description says '... imagine a creature so pure that it almost makes you blind with the light of its pureness? ...' The correct word should be 'purity'.