The Fire in Vengeance by Sue Wilder

There is love that lasts for a moment Love that lasts for a lifetime. But this love…this love has lasted for centuries.
Secrets have been hidden in a past life, putting Lexi in danger, and Christan—the immortal enforcer, the origin myth for the most feared creature in the ancient world, the man who loves her—must face what he can’t control in order to protect her.
The action-filled paranormal love story described as “enthralling” began with The Darkness in Dreams. The story continues. Lexi struggles with the reality—she is immortal, but her human vulnerabilities put her in danger. Christan now possesses a power he should not have. And the Calata is not pleased.
When a girl is murdered, Christan and Lexi are forced to return to Florence, where old enemies await and the Calata war erupts in a crimson mist. A past life must be remembered, clues hidden for centuries unearthed, while an ancient magic threatens to unleash the Fire in Vengeance to sweep across the land…