Let's see, since you're getting one of my characters (Carrion), Vicky, I believe you know pretty much all about his personality: plays the gentleman, hides inner psychopath, and loves to scheme/experiment.
Mitchell is a lot of hot air and has a short temper, and is very protective of others that he cares about. Walter can accidentally make things spontaneously burst in fire when angry, but not be able to actually make fireballs, infernos etc. (Fires will also quickly be put out because it needs Mitch's actual energy to sustain it, not Walter's).
Emerald is lascivious, bitchy, and likes to ridicule others. Her powers with plantlife won't transfer to Zefiris, but Zefiris might feel the desire to make poisons and have a fascination with daggers.