I've always believed it was a true vampire, summoned by Angelique in the form of a bat. And I had hoped that that vampire (the true creator of Barnabas) would someday return to the storyline. It would have been interesting to explore his history, where did he come from, and how did he get hooked up with Angelique?? And how interesting if he were actually "younger" than Barnabas -- I mean Frid/Barnabas in his forties, while the "other" vampire might have been quite young, perhaps in his early twenties.
What if this vampire still existed in 1970? I'd have loved it, if the series had explored the relationship between Barnabas and his "vampire father." He'd have been so much "older" than Barnabas, but in the body of a younger man. And, he'd have so much to teach Barnabas. And his history, of course, would have been completely different than that of Barnabas -- another story to tell.
This character/actor could have been the next Quentin -- another "insider" to carry the story forward in 1970, rather than the constant time-travel. I enjoyed most of the time-travel on DS, but it got to the point that EVERY storyline depended upon time-travel. It all became far too predictable. The writers should have been more creative, and allowed more action to take place in the "present," after the 1897 story. Exploring the vampire who created Barnabas might have been interesting.