The Cellar Demon, was the unseen villain in the episode "The Tale of the Dark Music" It's unknown who provided his voice.
BiographyWhen the Demon chose to live in the root cellar is unknown, he is motivated by music. Whenever music is played slowly he would open the root cellar door and prey on whatever human was nearby. The longer the music played, the better the chance of it opening the cellar. Also the louder it was the more powerful it would become. It has pierce glowing red eyes.
Years ago a man named Niles moved into the house. There he met it and he made a pact with it. The condition was that as long as Niles lured him humans to eat, he would get anything his heart desired in return. This man Niles became very wealthy and he never had to work or leave the house ever again. The people in the neighborhood all thought he was very creepy and a nut bag. When Niles passed away from old age, the neighborhood all lived happily again (according to the neighborhood bully Koda).
Soon the house was inherited by Niles' Niece and her two children Andy Carr and Christina Carr. They knew nothing about the demon, let alone anything about their Uncle Niles. Andy soon realized that every time he played music, it would open its cellar door and come out to prey. It is very good at illusions and manipulating people and putting people into trances. The demon at first seemed to be taunting and preying on Andy. It was constantly trying to hypnotize or entice him to enter his cellar. Possibly, since it didn't trust him yet, it was just playing nasty tricks on him to scare him.
Although terrified of the monster Andy, eventually decided to use this Demon to get his revenge on Koda (the neighborhood bully who was beating him up all the time). Andy filled the basement with a bunch loud speakers and various other music playing instruments. Then he wired them all to play together at once.
Then Andy lured Koda all the way home and locked him in the basement. Andy locked the cellar, and ran inside to turn the basement's power switch on. The basement was filled with full blast ear splitting music. This demon behind the cellar door embraced the full blast music. Then it glowed in a red aura coming through the cracks in the door and opened it faster than before. Then it closed in Koda who gave a terrified look and screamed as it delightfully ate him.
Then Andy turned off the music thinking Koda learned his lesson and went to get him out. He didn't hear from him or see him. Worried Koda might have been hiding, he warned him he would do it again if he'd hurt him. All Andy could find was a beautiful new bicycle this demon gave him as a reward.
Andy turned on his stereo again and the music quietly opened the door this time giving off a slight blue glowing aura. This time it was very nice and humble (possibly now because it trusted Andy or he had just been joking and teasing Andy before).
The it informed him that his great uncle before him who made a pact with the monster. So now he could do the same thing. The pact was that anything he ever wanted again he could get from this monster. Just as long as he would keep feeding him more humans.