As much a separate game as a period supplement, Vampire: The Dark Ages is a Dark Medieval roleplaying game produced by the White Wolf Game Studio based on Vampire: The Masquerade.
Vampire: The Dark Ages is set at the close of the 12th century in medieval Europe. It is advertised as a "storytelling game of Gothic horror." The game rules are based on a version of White Wolf's simple Storyteller system. The core book has a MSRP of $29.95 USD and is nearly 300 pages long, containing chapters dedicated to European history, descriptions of vampire mythology, vampiric powers (called Disciplines), and much more.