Devils

In the Devils' Line universe, devils are a subset of human that share a lot of similarities to vampires, but are more similar to humans. They live normal lives identical to those of humans except that if they see blood, they transform into monsters and lose control, causing them to attack and suck the blood of those around them.

Appearances
Normally, the devils' appearances do not differ from humans. They are biologically very similar to humans and have characteristics of what every human has. However, it is notable that non-blood-drinking devils have heavy dark bags under their eyes, which is a way to identify them. Devils who drink blood does not have eye bags, such as Johannes Kleiman, and some devils also choose to use makeup to hide their eyebags, such as Juliana Lloyd. When devils transform, their face and body features change drastically. Their eyes will turn red with veins sometimes appearing around the eyes. Their teeth will sharpen into fangs and their nails into claws.

Johannes Kleiman is the only (half) devil who only has one transformed eye.