Book 3 in Legends of the Romanorum:
Lance Shaw has achieved the impossible: secured an interview with the enigmatic and reclusive leader of the Inferi Brotherhood, a splinter group of vampires that broke off from the Romanorum in the 13th century.
When he meets Triarius, he’s instantly intrigued. The vampire is petite but possesses a personality that far exceeds anyone Lance has ever known. Triarius isn’t beautiful by any means, and the silver mask he wears over half his scarred face attests to the brutality of his world. But just when Lance thinks he’s done, Triarius changes the game. Abducted and dragged deep beneath the Snowdonia Mountains in Wales, Lance discovers an entire world no one has ever seen, and, in time, he discovers the true man behind the silver mask.