Resurgence by Catherine Lievens

The darkness is free, but the light is fighting back.

Apophis escaped the darkness, and there’s nothing Barnaby can do about it. He’s not a god—he’s human, and he’s a dead human at that. He doesn’t like feeling useless, so he spends his time at the bedside of an unconscious Thoth, keeping him company while he heals.
Thoth’s throat was slashed while he tried to keep Apophis locked in the darkness, and when he finally wakes up from his healing sleep, he finds that everything has changed. Apophis is free and is already using his demons to terrorize the human realm. He won’t stop there, which means Thoth has work to do.
Thoth is the god of magic, and he’s the only one who can seal off the demons in the underworld and stop Apophis from using them. It won’t defeat him, but it’s a start, and an advantage they need if they want to win this war. When Apophis sends a demon to kill Thoth, he goes into hiding, and he’s not alone.
Barnaby wants Thoth to be safe, and not even being in the same city where his murderous ex lives will stop him from hiding with him. Being stuck together in an apartment pulls them closer, but with a war brewing, there might not be a chance for them to be together.

Or to survive.