Sorry for the late reply, life is insane! ;n;

Yeah, magic's allowed. :) And races other than human, and enchanted items and et cetera. My biggest hope is that everyone gets creative with it, as you say use the power of your imagination! So, instead of a classic vampire, lets say, its a reinvention of the old concept. Feeds off oils instead of blood or something. 

As for a plot, I do have an idea where since Arom feeds into multiple universes, one such universe is letting evil into the city, creating a incresingly hostile enviroment. However, there is a way to stop these things from entering, but there cannot be any living one in the city already, so the rest either have to be killed or returned to the universe from where they came. This will allow characters to hunt these things, help with the ritual needed to close off the other universe, or perhaps work against the city, preventing the ritual from happening and allowing evil to take control of Arom. 

But, this is just one idea. I'm open to any other suggestions, if there is still interest.