Yeah, I'm thinking of having a fairly high cost, It would probably be more effective that the dark dragons, if not countered. I think a cost around there might be good, but countering it is so easy, I'm not sure. Also something would have to be done so it couldn't be made immortal.
The other thing I was noticing is that dark needs another creature type, preferably somewhere in between minor vamps and dragons. I was attempting to fill that need with this card, but I don't think I suceeded, the card would probably end up too powerful.