There are two things that I think are buried in the GM rules a bit that I want to flag.
*Masks*, p136, “Make a move when…”:
> You make a move—as hard or as soft as you like—when:
…there’s a lull in the conversation.
…a player misses a roll.
…a player hands you a golden opportunity.
*Masks*, p155, “Villains”:
> Villain is a catch-all term for the main antagonists in your story. Sometimes villains are straight-up monsters; other times, they have all too human motivations. You might even have a “villain” who’s actually one of the city’s biggest heroes! A villain is simply an NPC important enough—and threatening enough—to get an in-depth workup as an antagonist in your game.