For context, during the "Satanic panic" of the 1980s, it was a popular fear that every kids' hobby, from music to comic books, was driving them into the arms of the Dark Lord. One of the targets of this fear was Dungeons & Dragons, the tabletop game in which people harmlessly pretend to be wizards and knights slaying imaginary orcs. Because only Satan would design a game wherein you have to throw tetrahedral shapes in order to correctly use your imagination.
In the film, Hanks plays a kid named Robbie who becomes so obsessed with pen-and-paper RPGs that he quickly loses his grip on reality, eventually believing himself to be an actual paladin and suffering hallucinations of a Roger-Corman-style rubber monster suit he calls the Gorvil.
Look, it's a made-for-TV movie; they had to cut some corners on character names.
Things get even more out of hand when Robbie gets mugged in the street, then stabs his assailant because he thinks he's being attacked by the Gorvil (although stabbing someone who is trying to mug you is not entirely out of line).
"I attack with my Dagger of a Thousand Shankings!"