Entice Me at Twilight - Shayla Black

Simon Northam, the Duke of Hurstgrove, straddles two worlds. Born into the British peerage and a life of luxury, he believed he knew who and what he was--until he found out he was a wizard, that is. As a new member of the Doomsday Brethren, Duke must conceal his new identity from his family...and from his brother's fiancee, Elisabeth, the woman he wants as his mate. But there's more to Elisabeth than Duke knows--she's an Untouchable, a human completely immune to magic. And Mathias needs her to help him open Morganna le Fay's tomb and resurrect the ancient witch. Now, Duke must find a way to stop Mathias, protect Elisabeth, and make her his mate before it's too late.