Dark Peril by Christine Feehan

Dominic of the Dragonseeker lineage, one of the most powerful lines the Carpathian people has, ingests vampire blood laces with parasites in order to be able to go the very heart of the enemy camp and learn their plans. It is a one way mission. He knows he has little time once the parasites and the blood go to work. He plans to get in fast, relay the information to the leader of the Carpathians living in the area and go out fighting—an honorable way to end his life.

Solange Sangria is one of the last of the jaguar people, a royal pureblood. Her people, once many are now nearly extinct, a dying species that cannot recover from the choices they made over hundreds of years. She has long been alone, fighting to save the remaining women who are able to shift, from the hands of Brodrick the Terrible, her own father who slaughtered her family and everyone she loved. Wounded, weary, she plans one last battle, hoping to stop the man who has made an alliance with the vampires, accepting she will not come out alive.

They are two warriors who have lived their lives alone. Now, at the end of their time, they find each other, a complication, neither saw coming.