Demidevils are half devil half human creatures.They are made evil,and are kind of like the Anti-Christ,a demon who was handpicked personally by Lucifer to reap havok on Earth.The other Demidevils are sent to Earth to also reap havok in TDDA,but TDAAA will not let the humans down.
This drawing shows the Demidevil Kyoshiro destroying a town.