Magic at the Gate — Devon Monk

Allison Beckstrom is a Hound: She uses her magic to find unscrupulous magicians and stop them from harming innocents with their power. But every time she casts a spell, she places her mind, body, and soul at the mercy of magic, which uses her as much as she uses it....

Allie's lover, Zayvion Jones, is a guardian of the gates, imbued with both light and dark magic, and responsible for ensuring those energies don't mix. But Zayvion lies in a coma, his soul trapped in death's realm.

To rescue him, Allie must follow the specter of her deceitful late sorcerer father, Daniel Beckstrom, who is more than familiar with death's domain. And when Allie discovers that the only way to save Zayvion is to sacrifice her very own magical essence, she makes a decision that may have grave consequences for the entire world....