Sleep Killer are predatory creatures that resemble hairless, digitigrade humans, possessing an elongated face with
 a mouth lined with needle-like teeth. On each hand, they have five claws. SCP-966 feed on medium-to-large-sized animals,
  including humans. They hunt either alone or in pairs. Their hunting methods consist of emitting a single burst of
   an unknown type of wave, which permanently inhibits the ability of the affected creature to enter any sleep stages.
    The effective range of the waves is up to 6 meters; however, tests show that they can be blocked by
     post-transition metals, particularly lead. All attempts to make victims of SCP-966 sleep have failed.
       After depriving their victims of sleep, SCP-966 will stalk their prey until the lack of rest incapacitates it.
        SCP-966 have proved to be very agile and silent while stalking their victims.
        They will attack the victim when its health is very low.
        They can be seen via Night vision goggles.