The horned serpent's gem flashes, bathing a 30-foot cone in iridescent light. Each creature in the area must make a DC 17 Constitution saving throw. On a failed save, a creature takes 35 (10d6) radiant damage and is infected with the corpse cough disease (see the Corpse Cough trait). On a success, a creature takes half the damage and isn't infected with the disease. Gem Gaze has no effect on constructs and undead.