Board Thread:Dragon City Questions & Answers/@comment-101.161.41.54-20130531042203/@comment-9946604-20130531235557

You need to mix Nature and Lightning. You can't breed them directly so at least one parent must be a hybrid that has either nature or lightning in it. There is also a random aspect, so your chances are low. You may have to breed many times.

For more info, check out Breeding.