Board Thread:General Discussion/@comment-69.136.247.156-20151027043341/@comment-25479664-20151206224544

Well Mercury probably has ADD/ADHD (won't go into it TOO much because of wiki rules), but that just causes the inability to focus, impatient tendencies, and hyperactiveness (the last from ADHD only). However, that (rather obviously) wouldn't cause that sociopath-like nature. Maybe Cinder somehow brainwashed them or something like that from an early age, molding them both into killers. I'd especially see that with Emerald, as Mercury just seems to be in it for the thrills, and maybe some more earthly rewards (namely money, as he doesn't seem like a very power-hungry guy).