The term 'Monster of a Lizard' is referring to the GILA Monster, a species of venomous lizard native to the southwestern United States and northwestern Mexico. The GILA Monster is the only venomous lizard in the United States and is one of the two species of venomous lizards in North America. It is a large lizard, growing up to two feet in length, and is easily identified by its bright orange and black coloration.