The Demigod by Jessica Gadziala

Daemon never really liked his job in Hell—too much screaming, not enough partying. The human plane suited him just fine—more fun, less responsibility. That is, until the ‘old gods’ started waking up. Now the world he’s begun to love is unraveling. And to top it off, he’s been kidnapped by some of those power-hungry deities.
He never thought his salvation would come as a beautiful woman cloaked in shadow.
Nox is a demigod with a plan: free her imprisoned sister and bring balance back to the world before their siblings ruin everything.