Matt Marwick, formerly known as Boy 411 in the Young Army, is twin to Mandy and Marcus. His father was a Guard sentenced as a traitor. His three sons were sent to the Army. After the fall of the Custodians, Matt and his brother Marcus began working at Gothyk Grotto. Just before The Castle was overrun by the Darke Domain, Matt brought Jenna and Beetle to see Mr. Igor, the owner. Later, he, Marcus, Mr. Igor, and Marissa hid from the Domain in a SafeChamber.
Mr. Igor always calls the boys by the opposite name because he is convinced that they swap names to play a joke on him, even though they never try to.
Matt is identical to his brothers. When Jenna and Beetle first see him, they mistake him for Wolf Boy. Later, when Beetle meets Marcus, he thinks he is talking to Matt.