The Sapphire Crescent

The Sapphire Crescent, by Thomas M. Reid, is the first book in the Scions of Arrabar trilogy.

"The Sapphire Crescent

A mercenary order sworn to defend a god, but bent to the will of mortals.

When family turns on family, it's business as usual in Arrabar, but when a family turns on itself, an entire nation may be torn asunder."