The Ice Demon was the disguise of Mr. Forester, a park ranger.
The Ice Demon is a bluish-white humanoid with a body which appears to be made of ice. It had blue horns and eyebrows, red eyes with yellow sclerae, a pointed head, and a jagged mouth and chin.
The demon was sinister, but not very bright. He was easily spooked by the sight of Daphne Blake wearing hair rollers and a facial mask, and the gang used a flashlight to fool him into thinking a train was coming at him at one point.
Powers and abilities
The Ice Demon could shoot ice out of his hands that could freeze whatever it hit. This was done with parts from a snow-making machine built into the costume.
A Pup Named Scooby-Doo
The gang decided to go on a vacation at Snowy Mountain Lodge. When they got there, they heard about the Ice Demon from Mr. Peterson, a man who wanted to buy the property and build a mall on it. The Morgansons, the lodge's owners, claimed that there was no Ice Demon, and the gang went to bed. However, the Ice Demon appeared in Shaggy Rogers and Scooby-Doo's bed and chased them around the lodge, shooting ice at them. Velma Dinkley deflected one of his ice shots back at him with a fan, causing him to fall down a laundry chute.
The gang woke up the Morgansons to complain about their false claim regarding there being no Ice Demon. They confessed that the demon had been scaring their customers away for months, killing their business. The next day, the gang met Mr. Forester, a ranger who wanted to buy the land and build a park, and learned of an old mine that used to have gold in it. They decided to check out the mine, only for the Ice Demon to start an avalanche. They escaped from the avalanche and found the mine entrance.
When they entered the mine, the Ice Demon came after them again. They tried to get away, but he froze the exit with his ice powers, then proceeded to freeze the gang. They used "Getaway Plan #62", which involved Scooby coiling his tail into a spring and the gang simultaneously leaping backward. They sprung into a wall, breaking themselves free, but Scooby's feet were still frozen. Despite this, they managed to get away from the Ice Demon after much chasing around.
They set a trap for the Ice Demon, acting as if they had found diamonds. The demon took the bait and came after Scooby and his bag of "diamonds". He was lured into the beam of a heating lamp, causing the Ice Demon to start melting. The demon fled, and the gang chased after him with the lamp. They chased him into the ranger station, where they found Mr. Forester. He exclaimed, "Quick, he went that way!", but the gang weren't fooled; the Ice Demon costume was right next to him, and he was still wearing the feet. Forester tried to run, but Scooby caught him by using his own costume against him, freezing him in his tracks. It turned out that Forester had discovered that the mine was full of diamonds, and he wanted the Morgansons' land so he could claim ownership of them.