"Dark Challenge" is the 5th book in Christine Feehan's Carpathian series. This story focuses on Julian Savage, an ancient Carpathian, and twin to Aidan, who was featured in Dark Gold. Like all Carpathians, Julian drinks blood; he can shapeshift; he is telepathic; and he can not go out in the sun. The males of the species lose their ability to see in color and can no longer feel emotion after their 200th year. Julian is around 800 and is ready to end his existence. If a Carpathian man goes too long without emotion, he can turn vampire, an evil beast who kills without discretion. The only way to avoid that (or suicide) is to find his lifemate, the other half to his soul.
At the end of [b:Dark Magic|287633|Dark Magic (Carpathians, #4)|Christine Feehan|http://ecx.images-amazon.com/images/I/51bx3ZonuXL._SL75_.jpg|2830894], we discover that a group of fanatical human vampire hunters have targeted some Carpathians and other humans for destruction. A beautiful, mysterious singer named Desari is on their hit list. Ancient Carpathian Gregori has asked Julian to seek her out, warn her of the danger, and protect her. Once he finds her, Julian realizes she is his lifemate.
Moments later, Desari is shot during her performance. Julian saves her life, but is attacked by a strange leopard who is also trying to protect her. We later find out that the leopard is Darius, Desari's brother. The two of them, and the other three members of their band are all Carpathians. But they grew up separated from the rest of their people. Hundreds of years ago, when humans were attacking their kind, they escaped. They were all children, but Darius took care of them... and has done so all these years.
The relationship between Desari and Julian develops quickly. It's nice to see the heroine as a grown, secure woman. Someone who is already Carpathian. So many of the female leads in the series are mere babies compared to the age of their lifemates. Desari is an ancient in her own right. And Julian isn't nearly as obnoxious as some of the Carpathian men we have encountered before. They have great chemistry and sexy love scenes.
Of course, where Carpathian women go, so goes the vampires. So Julian must band together with Darius to help protect Desari and the other female in the group. The task is even more monumental since Julian, himself, suffers from the taint of a vampire who forced a blood exchange when he was just a young boy.
This is one of my favorite books in the series. We get to meet a wealth of new characters and we get backstories on so many characters that will be featured in the future: not just the band members (some of whom we find out are long lost relatives to Gregori), but also the ancients Gabriel and Lucian. My only disappointment here is the missed opportunity for the reunions between Julian and Adian --and the members of the Daratrazanoff family (yes, that's last name of Gregori's people... although we don't learn it in print until several books later.)