[Sarah54321]

Okay, so, on my Umbral, I cannot transform into a vampire. Not that I was wanting to, but I was wondering if that was lore wise. I thought that only Doriads, Glykin, and Mechanations couldn't transform, is all.

[Ryu-Kazuki]

Corrupted can't become Vampires. This also applies to Papilion, Shaitan, and Oracles.

[Blissey]

Vampires are sort of already Corrupted anyway, or I guess in a more consuetudinary term, Converted. I assume they're just Ancients because they can get old, and have been around as a race for a very, very long time.