(ART) FANFICTION COVER

My trio of original characters, Steve, Erwin and Nicholas, have been put into Geronimo Stilton's Kingdom of Fantasy and now they must survive. The series of events in this book follow the main storyline of the first book about this kingdom, but this time it was confronted by three adolescents, two of which with supernatural powers. How would they mess around? What could go wrong? And most importantly, will I get bashed for character-inserting my OCs into a story without changing the main plot and call it a fanfiction?