A Vandel is a type of monster. It is a portmanteau of the words "vampire" and "devil".

Beet slaying a Vandel

They had been causing mayhem which made society collapse and the dark age begin. Vandels often are slain by Vandel Busters. Riku Sanjo and Koji Inada said that they did not base the Vandels off of any particular mythology. The two approached the creation as if they were making a "new myth." They developed each character from one purpose or idea "as an axis." The fears of vampires and devils inspired the "image source" of the Vandels.