Board Thread:Dragon City Gameplay Questions & Answers/@comment-41.129.61.114-20130619200125/@comment-10090661-20130620042300

Crystal = any two It's pure luck whether you get a legendary type or any dragon with one element from each parent. (More likely the latter.) Using 5 gems for breeding boost helps a bit, but it is still no guarantee.

Pirate = Any Sea hybrid + any Dark.hybrid. It is also possible you may get a Petroleum Dragon instead, or some other random dragon with one element each parent. Again, it's pure luck.

So, GOOD LUCK! =D