Possible idea for Death Knight Class Campaign for the Death Knight Dragon Mount?
I could see them going to Dragonblight to raise some dead red dragon there, but you see Alextrasza the Lifebinder as the player and she eyes you with suspicion.
Then some demons invade the place and with the chance you decide to help her out than raising the dragons at first.
She thanks you for helping you and you ask her if it is ok for raising the dead red dragons for the cause against the Burning Legion.
She tells your actions in the raising the dead like the Lich King will cause the other factions to be not in terms in the Death Knights and you as Deathlord.
Then you accept the mount and Alextrazsa wishes you best and flies off. Some Death Knight comes through the portal and asks for your presence back home.