Stained Glass Monsters. Eferum, #1

Creatures from the Eferum are a world-wide problem: creeping through tears in the fabric of space, they feast on every unprotected human they can find. Tyrland has a solution in the Kellian: faster and stronger than humans, they are Tyrland's clawed, shadowy monster hunters. But no matter how faithfully they serve, or how true their sworn word, they are too different, too separate, to ever be entirely trusted.
Rennyn Claire is a complication. Secretive and obscenely powerful, she knows entirely too much about a massive new threat to Tyrland's safety. Worst of all, she is linked to a past that the Kellian would rather forget. All three of these things - monsters, Kellian, and an entirely overpowered mage - are about to land in Kendall Stockton's lap. The last thing Kendall wants is to try to play conscience to someone who can swat her like a bug.
But innocent lives are at stake, and no-one else seems willing to ask if what is necessary is the right thing to do. And who, exactly, is the monster?