Sergi by Kim Allred

A secret lab hidden deep within the Carpathian Mountains.
A vampire on his own—until the beast comes out.

Everything the Vampire Council had hoped to keep hidden is slowly being unraveled. Devon Trelane requires documented proof to tear it all down and declare war against House Venizi. The mission is clear. Locate the secret lab where Venizi is creating Magic Poppy, the addictive potion that makes vampires go mad.
For centuries, Sergi has been bodyguard and cadre in service to House Trelane, more specifically, to Devon Trelane. But, as an ancient, time is catching up to him.
He needs this mission. Not only to protect the vampire race but to prove something to himself.
Shifter 473 has been a prisoner in a vampire laboratory for months, surviving by sheer will and plenty of luck. Once filled with hopes of escape, there wasn’t much she could do toward the effort when locked in a cell for countless weeks.
After months of near solitude, she’s deemed submissive enough for a work assignment. It’s not the reprieve she hoped for when she learns the truth about the horrific experiments being performed on shifters.
When she discovers a vampire being held prisoner in the lower depths of their prison, she has a decision to make.

Will he be the shifter’s salvation or their damnation?