You can only stare in horror as the person in front of you begins to twist and distort, their face melting away to reveal a constantly shifting visage, with the only constant being an unnaturally wide jaw, filled with long, sharp teeth. The pained screaming is constant, the once human voice shifting into something that sounds more like a reptilian screech. As they clutch at their head, they fall silent for a moment, their clothes hanging ragged and torn from their now grotesque, misshapen body. Finally they look up at you, one eye almost human, the other gleaming red. Then, they charge. Instinct: To lash out from the pain

• Bite with huge jaws
• Choke with hands

They come at night, scratching at the locked doors, howling and mindless. No-one alive has seen them up-close; not their mottled, grey flesh, their emaciated forms, the claw-like nails erupting unnaturally from the tips of their fingers, not even their blood-stained, needle-like teeth. The only familiar part of their appearance is their infamous eyes: huge, yellow, pupil-less and glowing in the darkness. Instinct: To tear the living limb from limb

• Tear through flesh
• Howl with fury
• Charge on all fours