Hmm.

[This is so much easier to focus on. Alucard's eyes close, summoning memories of all the books in his father's library. The dark but not too dark ones, identifying all of the night things roaming Europe. He hears pounding hooves in his mind again and...there. That's the image.]

They were not armored skeletal things. Just men upon their horses riding through the night sky over the land. Usually identified with olds Gods rather than the singular Christian God, seen as an omen or harbinger. A similar iconography to yours, but not precise. And not common either, at least by my time and place.

[Now he'll drink. Slower this time, the pace of his heart no longer thundering.]