Damned by the Ancients. Nemesis of the Gods Trilogy, #3

Vienna, 1908: Gabriele Ziegler is a young art student who becomes infatuated with charismatic archaeologist Dr. Emeryk Quintillus. Only too late does she realize his true designs on her. He is obsessed with resurrecting Cleopatra and has retained the famed artist Gustav Klimt to render Gabriele as the Queen of the Nile, using ashes from Cleopatra's mummy mixed with the paint. The result is a lifelike portrait emitting an aura of unholy evil...
Vienna, 2018: The Mortimer family has moved into Quintillus's former home, Villa Dürnstein. In its basement they find an original Klimt masterpiece-a portrait of Cleopatra art scholars never knew existed. But that's not all that resides within the villa's vault. Nine-year-old Heidi Mortimer tells her parents that a strange man lives there. Quintillus's desire to be with Cleopatra transcends death.
His spirit will not rest until he has brought her back from the netherworld. Even if he has to sacrifice the soul of a child