Wrath for sisterly things, and I can see Wrath definitely using Luna for any information relating to any future case she starts working on once she graduates and starts a career as a PI or assistant to a PI/detective. That and she'll always be willing to listen to her insights on how somebody may have died. Digging in bodies may creep her out a bit but she'll learn it's valuable to know how a person died. (I also love Dexter!, great series/books)

Edgar Minks could be somebody she runs into, directly or indirectly (either as his alter ego Leon Minks, or as himself.) He's definitely the sort to charm and seduce women not to mention he's plenty sinful but so far isn't known to have killed anybody. He could potentially be a victim either she kills him in the end or it's a near miss. Several ways this could go so if interested we can brainstorm ideas and see how this'll end up.

Walter Staghart I offer as somebody who could use her to learn more about murdered victims, potential hurling as well, though he's working class, he does have a good paying job (auror) and he probably seem.... odd to her, given he's doesn't feel emotions too much (I loosely based him off Dexter too...just without the serial killer side, plus a mix of a few other inspirations). A part of me would be amused to see a serial killer and an Auror becoming strong friends and/or romantically involved.