There is a difference between (a) reading stories in which there is incidental presence of unlawful matters and (b) writing such stories.
1. There is nothing in of itself wrong with coming up with imaginary worlds. 2. Description of bloodshed is permitted if it is restrained and within the limits of decency and the dignity every human (and, in fact, living) soul deserves. 3. Characters can be described, but within the limits of restraint befitting the description of others (e.g. can't describe the specifics of the `awra (private area between the navel and the knees) or beauty of others, though general mention of them being beautiful, etc, in restrained and dignified ways would be permitted). 4. It is not permitted to write about unlawful situations in specifics.