Demon is a demonic sergios and Sally's pet. He has purple skin, white head, black and white horns, and yellow eyes.
While in the Monster Hunter universe, the team comes across a fighting arena created by hunters. They infiltrate the arena by putting their own rescued beasts into the fights. They all only pretend to fight each other to give the others time to rescue the trapped beasts. Sally rescues Demon and he's grateful.
Demon initially displayed a shy personality, as when Sally freed him of his cage, he merely took a quick look around before hiding out of sight in a shadowy corner. When Sally pet him, he then showed a mellow nature, chattering to himself and twitching his head around. Unlike other dragons in the series, he doesn't attack on immediately coming across danger.
Demon can release purple spheres of poison.
Trivia:
Demon gets his name from him being a demonic sergios.
Sally states she likes Demon is because he's purple, her favorite color.