Awesome!
It somewhat seems to be very similar to the Dark Angel though, in class, stats, abilities etc. But if I had to choose between those two I would chose the lich.
Also it seems to be a quite powerful unit, but they should not be too easy to attract either. Maybe some harder requirements? I mean, you build a graveyard anyway for vampires, and then suddenly you have the opportunity to get two kinds of high level creatures at the same time very fast. Imo, it would get more fun with this kind of continuous goals.
Anyway, a very interesting idea, work on the details and I think this will be a good competitior for eventually new units.