Of Song and Scepter by Liesl West

She’s a killer in disguise. He’s determined to make her his queen.
As a deep sea death-dealer, Enna Valomir’s life is simple: kill the siren, deliver the body, collect the reward. There’s just one problem. Enna owes a mermaid her life, and in the cutthroat waters of the Abyss, that’s a lifelong blood oath of service.

When the mermaid orders her to kill the Abyssal Princess, Enna is pulled into an impersonation scheme with no choice but to infiltrate a gaudy surface court and help the mermaid win the heart—and throne—of its unwitting future king.

But Prince Soren isn’t interested in courting the so-called Abyssal Princess, or any power-hungry princess, for that matter. He’s finally met his match in her fierce and mysterious handmaid, and he’ll be damned if he can’t have Enna for his queen instead.

Breaking a blood oath means death, but Enna falls for Soren anyway. Now she must watch him descend into a ruin of her own making, or warn him of the ruse—and die.