The Burning Throne. The Burning Throne, #1

The Empire is a place where no secret is safe and blood drenches every surface. Lies, royal parties, and iron-fisted monarchs are the norm. After all, you can't party when you're dead and murder is something to be expected, not feared. Nate, heir to the Throne and son of Lucifer IV, watches his mum die in front of his eyes, helpless to stop it despite his best efforts. He wants revenge, but to get it, he needs confidence and a partner in crime.
His father, thankfully, decides to find him a Princess to continue the family line, that if successful, will allow Nate to get the revenge he craves. Lexi, runaway assassin, armed with a secret and the expertise of a murderer, and just wants to find a job that will give her more and help her get revenge on her sister. Taking the first step, though, is difficult. But when she hears rumours of a trial being conducted, she awaits the battle of a lifetime and agrees to form an alliance with Nate.
Problem is, she needs to hide her identity from him and Lucifer until the job is complete - knowing she's a Hybrid could get her killed, and no one wants a dead assassin.