Shar is an infamous god and Faerun itself is much smaller than Earth; most folks of the Realms are aware of the Mistress of the Night and her malevolent nature. If a DM or video game doesn't make such knowledge freely available up front, then a trivial Attribute or Skill roll should be adequate to address any momentary player ignorance. There are many topics that merit protracted discussion...this isn't one of them.
