A Martian Devil (simply known as a Devil) is a monster that lives on Mars & is similar to a ghoul.
Unlike ghouls, with blank eyes, devils tend to have slits for pupils & are humanoid for their whole life.
Devils have the abilitys to change humans into devils too. There are two ways
One way a devil can transform humans is blood biting, which they'll bite the human & begin drinking the bleeding part. When this happens, the human will faint & simply die, then they'll reincarnate as a devil. A perfect example is when Bart Sampson revisited Mars & met a devil, who tryed to suck blood from his hand.
The other way a devil can transform humans is blood kissing, which they need to transfer a sample of their DNA into the human, which usually, they'll do it by kissing a human & their saliva will go into the human & they will die & reincarnate as a devil. One example is how a devil tryed to kiss Bart on the same trip after failing to get his blood.