Well I have been considering a character which could fit nicely into the current cast and have some role in the ensuing chaos. 
So far I have thought of two, firstly a human serial killer, sophisticated and insane to the highest level, not directly involved in anything - but a nice red herring perhaps especially for the detective types. Leaving bodies and crime scenes in his wake, his deceased wife (a fabrication of his mind, to him she is alive and with him still) is with him and the main cause of his psychosis. 

Or secondly a 'possessed' human psychopathic drug addict, perhaps working for one of the factions or as a mercenary type. Regular drug user of all types, using the boons they offer combined with his somewhat unstable companion - a demonic type entity which inhabits the shell of his mind, to compete with the otherwise more deadly other races throughout the city. The entity could have been 'obtained' against his will in a failed spell or summoning, and what is left of him is now split vying for control - something along those lines. 

Either of those sound appropriate? Any feedback or suggestions would also be very appreciated.