Beyond that range it is considered blinded. Yrthaks are invulnerable to gaze attacks, visual effects of spells such as illusions, and other attack forms that rely on sight. An yrthak whose sense of hearing is impaired is effectively blind, treating all targets as totally concealed. Immune to mind-influencing effects, poison, sleep, paralysis, stunning, and disease. Not subject to critical hits, subdual damage, ability damage, energy drain, or death from massive damage.
Zombies have poor reflexes and can perform only partial actions.