I don't know if I'd consider the Gorgs to be monsters. The list people have given so far seem to include animal-like sentience (take that how you will), with the exception of Skenfrith, but as he's a shapeshifter you can't really peg him down to one particular type of being. If this is the case, then Gorgs are sentient beings who can operate on more than just an instinctive level. They have rules, motivations other than physical necessities, culture, etc.