My Immortal Assassin: Number 3 in series

All Grayson Spencer wants is revenge. Christophe dit Menart destroyed the life she loved and she wants the pleasure of killing him, no matter the cost to her. When her attempt fails, she is forced to turn to Durian, a feared demon and expert assassin. Newly armed with powerful magic she can barely control, she'll do whatever it takes to complete her mission - even surrender to a dangerous fiend whos eyes promise unimaginable pleasure.

Sword to protect all mages, Durian can't let Gray threaten the uneasy peace among demons, humans and mages. He proposes a deal: he'll train Gray to master her gift if she'll bind herself to him magically, submitting to his control. As Grays's powers intensify so too does Durian's hunger for her and when the dark mage, dit Menart, makes a final play for Gray, will the passion she and Durian share be the key to their survival or the seed of their destruction?