Dark Bringer

Gavriel Morningstar is Sion's chief archangel, a stern deliverer of justice whatever the cost. Known throughout the empire as Light Bringer, he is immune to mercy or lenience - and doubly so to human passions like love.
Cathrynne Rowan is half witch, half angel. Such unions are forbidden, and the offspring - called cyphers - are reviled as abominations. But Cathrynne's powers are indisputable, so when Lord Morningstar is nearly killed by an assassin, she's summoned to serve as his bodyguard....