The Tracer - The Rifters, #4

The portal connecting Earth to other worlds reopens, and Daelin Long stands ready to rescue her sister. After a winter of strenuous training, she's prepared to battle the evil her sister warns against.  Only, the rift is more unpredictable. The Mothman arrives whispering of death and transports Daelin to a land with seven moons. There, she faces a monster that can exist in two universes at the same time.
Refusing to believe her fate is sealed, Daelin searches for the way home. With only her staff, her wits, and an uninformed detective, she dares to lead the fight. Otherwise, her sister and Earth don't have a chance.