Mirror Dragon

Breeding
You can get a Legendary Dragon by breeding two Rare Hybrid dragons with each other at the Breeding Mountain or Ultra Breeding Tree. These are: Note that no combination is 100% sure when it comes to get a Mirror Dragon. It could just as easily result in a Crystal Dragon, a Legendary Dragon or a Wind Dragon, in addition to every whatever could be made from the elements used. Legendary dragons are hard to obtain and you need a lot of luck to get one.
 * Gummy Dragon
 * Cool Fire Dragon
 * Soccer Dragon
 * Armadillo Dragon
 * Petroleum Dragon
 * Pirate Dragon
 * Poo Dragon

The two most efficient combinations (in terms of time used) to use are:

Cool Fire Dragon + Cool Fire Dragon (4 Hours)

Cool Fire Dragon + Gummy Dragon (8 Hours)

Cool Fire Dragon + Soccer Dragon

Damage Calculator
Legendary type attacks do normal damage to all Elements and double damage to other Legendary. Legendary takes normal damage from all Elements, double damage from other Legendary and half from Fighting.

Counter Dragons
'''Any Legendary Dragons or Pure Dragons. Pure Dragons are better for this case.'''

legendary dragon + legendary dragon = pure dragon