The Ruby Dragon can only be bred in July by breeding a Scorch Dragon and a Chrome Dragon in either order at the Epic Breeding Island/Breeding Cave. The player must also be at least level 18 to breed it. The Ruby Dragon is one of the 12 original gemstone dragons.
Gemstone dragons such as the Ruby Dragon are difficult to breed because they have a much lower probability of being successfully bred, even when the correct combination of dragons is used. This probability is lowered even more due to the limited availability of gemstone dragons. Furthermore, even if a gemstone egg is born, it takes a very long time to incubate and hatch. The time is equivalent to one hour for every day in the specific month. The Ruby Dragon is available only in July, which has 31 days, and therefore takes 31 hours to hatch.
Ruby Dragons are meant to be very difficult to acquire because they generate gems rather than money like standard dragons. From birth until level three, Ruby Dragons generate two gems every month. From levels four to seven, they generate three gems every month. From levels eight to nine, they generate four gems every month. At level 10, they generate one gem every week.