Demons have appeared in two animations and a game. They are red men with horns, a forked tail and have big muscles. They have green blood. Some have wings, like the demon that appeared in Tribute, or the ones seen in the background of Hello Hellhole. Some demons can leave hell and have the ability to eat peoples' souls. In hell, they work in the Sinner Squishing rooms or they wander about, attacking sinners with weapons, but they don't harm the tourists. They seem to resemble the Imps and/or the Pinky Demons from Doom.
The demons made their debut in Tribute, where one demon, with big green eyes and a close resemblance to Tord, appeared in front of Edd and Majin and told them to play the greatest song in the world or he would eat their souls. The song was so great it ended up killing the demon, sending it back to hell.
When the Group went on a visit to Hell, they met some more demons as well as Lucifer, their leader. These demons have yellow eyes, claws, two sharp teeth showing and have large muscles. One can be seen in a hockey mask, wielding a chainsaw while chasing a woman and another is seen wearing a baseball cap while working in Sinner Squishing Room #666, he squashes Noggin with a giant mallet. Flying Demons with tridents are flying around in the background during the episode and gigantic green demons can be seen wandering through Hell.
An army of demons appear in level 1 of Bang, Boom, Splat! where Edd hallucinates that demons are attacking. These demons can fly, have goofy smiles, smaller horns, no tail, smaller muscles, spikes on their shoulders and murky red skin instead of bright red. They can be easily killed with one shot from a shotgun and are revealed to have green blood. Another leader also appears, who is much larger, with brighter skin, bigger muscles and bigger horns than his minions.
In the epilogue of Bang, Boom, Splat, once the player has completed level 4, Edd is taken away in the back of a van, tied up in a straight jacket. Suddenly the leader of the demons appears in front of him and the van can be seen driving into the distance. It is unknown what the fate of Edd or the demon leader was, but the demons haven't been seen since, the most likely reason is that they went back to hell.
Lucifer appears in Hello Hellhole. He is thinner and taller than most demons, he also has much bigger horns and claws, he wears black shorts with a skull on the front. He works in the Personal Hell section of Hell, and is annoyed by tourists. He also hates being called Lucy.
Demon from Tribute
This demon has a very close resemblance to Tord. He wears the same outfit as Tord and has the same hairstyle and facial features. He has bright red skin like most demons, but he has green eyes instead of yellow, this demon also has wings, small horns, which are red instead of white/yellow, like other demons, and a forked tail. He has the ability to eat peoples' souls, but has never been seen using this power. He appeared in a parody of Tenacious D's "Tribute".
This Demon leads an army of demons. He is a different type of leader to Lucifer. He has gigantic muscles, big horns (but not as big as Lucifer's), a larger head, bright red skin, two big horns on each shoulder, two sharpened bottom teeth and he is bigger than most common demons. Despite this, he can be easily killed by one bullet from a shotgun.