Fallen's First (Sins of the Maker, #1)

Saer—the first demon and Pride himself—exists for a single-minded purpose: harvest souls to feed the ailing Devil who made him. The same Devil to whom he has sworn a vow of absolute loyalty. 

Until the demoness Neyu, incarnation of Lust, makes Saer question what he understands his existence to mean. Every touch or glance from Neyu burns through Saer—the irresistible pull between them at blatant odds with his purpose…and his vow. 

One does not love another above the Devil without consequence, so when Saer surrenders to his feelings for Neyu, the Hells shriek—and he’s woefully unprepared to endure the punishment for his sins.