The Bloodstained Shade - The Aven Cycle

Latona of the Vitelliae, mage of Spirit and Fire, lies still as death. Her fate rests in the hands of her allies, who must redeem her soul from the churning void where Corinna, leader of a banished Discordian cult, has trapped it. Protected by a cabal of corrupt priests and politicians, Corinna plans her most daring assault yet: a ritual striking at the ancient heart of Aven, with the power to swallow the city in a maw of chaos and strife.
Her success would be Aven's doom, and the greatest violence would fall upon the most vulnerable. Before Sempronius Tarren can join Aven's defense-and his beloved Latona-at home, he must end the war abroad, outwitting the blood-soaked machinations of his Iberian opponents. His own magical talents remain hidden, but dire circumstances tempt him to succumb to ambition and use forbidden tactics to hasten the way to victory.
To defeat Corinna, Aven's devoted protectors will need to perform extraordinary magic, rally support from unexpected quarters, and face the shadows on their own souls.