Diablo has a voice and isn't afraid to use it. Which has caused quiet a bit of friction between him and the very old and very deadly witches and warlocks of the Mystical Hunt. All of them but one person.
Aikaterini has centuries of experience and trauma. She also has a tendency to disappear into her head. The new, outspoken man living in her castle forces Aikaterini to step out of the peace she has built inside of herself and into his arms. Warm, loving arms that are threatened, right along with everything else in the world, by the deadly and powerful Titans.