Its kind came out of a fiery chasm which contained an otherworldly portal. A furnace hotter than the sun burns within its chest. If it burns you, the pain will never fade.
Biology
Beliaddon is a large, bipedal Pokémon resembling a demon. It is mainly deep red in color, with black and red striped horns and a small flame sitting between them. It has narrow yellow eyes and a black mask-like pattern on its face, as well as sharp white teeth and a mouth resembling a beak. It has large black wings with fire tips, large hands with black patterns that resembles magma; this pattern also decorates other parts of its body. It has large yellow claws, a black circle on its stomach with yellow and orange stripes through it. It has feet resembling hooves, and a long red tail with a point on the tip with a flame above it.
The flames they breathe are astronomically hot, and a burn from them will leave the target in pain that will never fade. Beliaddon are also skilled swordsmen, able to wield large swords made purely of fire. Beliaddon will command groups of Fallengel to do its bidding. Through lack of a moral compass, they obey without hesitation. Its kind are said to have come from a fiery chasm from within an otherworldly portal.
The Devimp line is based on the popular interpretation of demons in religion. Beliaddon in particular is based on a demon lord or archdevil, or possibly Satan himself.
Name origin
Beliaddon is a composite of Belial and Abaddon. Those two names are often associated with either Satan himself or powerful demons under his command.