Their Promise by Catherine Banks

Three warriors. One princess. A darkness that binds them all. A promise waiting to be fulfilled.
When Princess Liliana of the Hybrids returns home, she finds herself being pursued by three powerful men from her past, her childhood friends wanting to complete a promise they made years ago – the protective jokester Kayden, the charming diplomatic prince Trey, and the brooding warrior Mason. Each man awakens something different within her, but also feeds the dangerous darkness she’s tried so hard to suppress.

As demon portals appear throughout their realm, Lily’s powers grow stronger and more volatile. The darkness in her suitors’ auras responds to hers, creating a dangerous and seductive bond that both thrills and terrifies her. But can she trust her heart when her very nature might corrupt the men she’s growing to love? Will embracing her darkness lead to saving everything she holds dear or total destruction?