Vampire dragons draw their magic directly from the Negative Energy plane, it's what powers most of their abilities allowing them to walk through shadows and turn into bats or mist like any vampire but for the vampire dragons it’s channelled through their breath weapons.

In Dungeons and Dragons it's pretty unusual for dragons to have more than one type of breath attack but the Vampire's have their original type and the Black blood vomit ability.

I couldn't fit it all on the single reference sheet... https://www.furaffinity.net/view/57097750/