Sephtis Vencel is the one that interests me the most, but Adrianna Wolfric would be fine with Abner.
With Sephtis Vencel I suggest Madara. He's based off of the Naruto character of the same name. His general info can be found here (but ignore all of the information regarding the war as my portrayal of him diverges after he finds Obito): http://naruto.wikia.com/wiki/Madara_Uchiha
I think that as soldiers they would both have many similar interests. Madara has been closely following the Purine/Imperial War going on right now and has been on the fence on which side to join after he and other shinobi were transported to this world via a jutsu. His goal is to amass more power before returning to his world in order to become the god of his world. I think it would be interesting for Sephtis to try and convince Madara to join his side of the war and maybe later on down the road to find out Madara's true intentions? I'm up for other ideas as well.
Abner VanSlyk is a vampire hunter, though his definition of a vampire is very broad. I could see him hearing about Adrianna Wolfric drinking blood and going after her, mistaking her for a vampire. They could get into a fight or "hunt" each other down. If you want to go with this one I'm really aiming for a more violent rp as really otherwise Abner would have nothing to do with her or any other nonhuman.