Annul

In Commander, Annul is a role-player rather than a staple — the artifact and enchantment density in most pods is high enough to justify it, but the one-for-one trade is harder to stomach in a four-player game where you're only answering one threat. It earns a firm slot in dedicated spell-slinger or spellcounting builds where every cheap blue instant does double duty. In Pauper it's a legitimate sideboard card against affinity and enchantress strategies, where hitting Sol Ring equivalents or Utopia Sprawl on turn one can decide a game outright. Legacy and Vintage run narrower, faster interaction, so Annul sees only fringe play against specific combo pieces; the competition from Force of Will and Flusterstorm is simply too steep for maindeck consideration.