Just because a monster is good doesn’t necessarily mean that they’re nice and Draco is the perfect example of that. He’s an imaginary friend who was actually very cheerful in his prime, but once his creator grew too old for an imaginary friend things went south fast. He spent every single second he had with his creator so when she abandoned him, it was like a part of himself was destroyed. He was so scared, lonely, and had no idea what to do with himself. His neighbors took notice of this and frequently tried visiting him to see if they could offer any help, but he absolutely hated the constant attention he was getting and begged to get his house moved to a remote location. It took an awful lot of complaining but eventually, he was moved to his own little area. Isolating himself and bottling up his feelings for years really affected him negatively, and turned him into a massive grump.