Viser is a stray devil that the Research Occult Club to show Issei how they operate.
She was marked to be hunted and killed because she killed her Contractor/Master and consumed human flesh after.
Viser has the appearance of a young woman with a great figure with long brown/black hair. Her lower body is that of a gigantic beast with four legs, each having sharp claws, and a snake as a tail. Her overall appearance is reminiscent to that of a chimera.