Want the fastest breeding comination to hatch a Bone Dragon? Not a problem, not a problem. The Bone Dragon was the first Limited Dragon in DragonVale, and has made two appearances (Halloween 2011 and 2012). Also, for a limited time it is back as part of the "Bring 'Em Back" event.
Breeding Pair: Blazing + Lava
Breeding Time: 10 hours or 8 hours (with upgrade)
Availability: Back till Jan 2nd
Type: Fire, Earth
Price: 25 Gems (Seriously consider buying, if this one gives you trouble)
With a low price tag, don't pull your hair out about this one. It is a super cool Halloween themed dragon to have though - hats off on a great design. Note that is possible to get this one while seeking Clover or Sakura during the "Bring 'Em Back" event - so bear that in mind.