Im guessing the DKs mount will be like the undeads, but with the armor of the palladins warhorse, but black ans silver armor. Id say thats the best guess soo far. Bliz said that the DK is just a pally turned bad. So, a warrior, but with like, evil powers and shit. But i think we can all agree that the DK will be damn awesome!

Its a Deathcharger mount every death knight will be able to summon the lvl 40 version of the deathcharger, and you would have to do a quest to get the epic version. So thats what it is