Several creatures in the D&D world live in dark caverns, and dank forests, and only emerge, when they decide to, in the depth of night. Those creatures, when in the full light of day (or a spell that generates light) might suffer some penalties to attacks, proficiencies, skills, and the like, due to impaired vision from the blinding light.


Goblins are the iconic creatures that suffer in bright light, taking a penalty to attacks and morale. Kobolds, orcs, and hobgoblins take the same penalty.


The "light sensitivity" trait on orcs caused the "dazzled" condition in bright light. While dazzled, the orcs suffered a -1 penalty to attacks and certain visual skills.