Even though I've run encounters with Piercers, I'd never noticed that "Miss:" was a formal part of their attack, but it is. One correction: a stackexchange post ( here ) identifies four "official" monsters using the syntax (although one actually uses "Hit or Miss:" ): the Piercer (MM), the Kobold Inventor (Volo's Guide), the Zorak Lifedrinker (Dungeon of the Mad Mage), and the Fluxcharger (Guildmaster's Guide to Ravnica). However, of the three I can check (I don't have Mad Mage to look up the Zorak Lifedrinker), none of them actually deal damage (except to the attacker) on a Miss. All of those can be handled in an NPC statblock by filling out the description and setting it to "Show" in the roll template. PC's have a similar "Description" field in the Attacks & Spellcasting definition on the front block. I can see where it could be useful for certain attacks (splash damage from a near-miss thrown container, for example), but that would appear to only be useful for homebrew (which isn't a complaint; I homebrew / modify a lot of my monsters, it keeps the players on their toes).
