Creatures of Forever (The Last Vampire #6)

Alisa has fought every battle, against evil, against hate, and even against death itself. Now she nears the end of her incredibly long life and another unexpected force emerges to destroy her, or perhaps save her. But this force... is unlike anything she has experienced before. It seems to emerge form another place, another world, where demons are potential saviors and the future of mankind is already wrapped in the ash of a forsaken hell. This force, these strange beings, present Alisa with hard choices. To save herself, or to save others and risk losing even her own soul. These beings push alias into a place where even the perfect feat to tread.