The Hazards Of Demonsummoning

Mark is the apprentice of a man only known as "the Warlock", but omnious as that may sound, Life as an apprentice is rather boring, so one day Mark decides to attempt to summon a demon. this do not go as planed.

written for the Knockouts, part two: write a story with the line "Mark! i told you not to do that!", wher it was the winning entry!