Board Thread:Dragon City Mobile/@comment-13641045-20140219172518/@comment-11259553-20140220144532

The fight you will have is based on how many Hammers you have saved up. If you have 0 it will be Viking, 1 is Poo, 2 is Firebird. So you can get through it only fighting those 3.

Of course you can save up to at least 12 (I crashed when fighting with 12 though, it might not be possible to go further). There's a different dragon for each number up to that point.