Glare of Heresy

In Commander, Glare of Heresy is a sideboard card stapled to your mainboard whether you like it or not — white is ubiquitous enough that you'll almost always have a target, but the narrowness stings when you're staring down a green threat instead. In Modern and Pioneer it's a pure sideboard piece, slotting in against white-heavy aggro and midrange strategies where exiling a Restoration Angel or Lyra Dawnbringer at instant speed for one mana is legitimately powerful. Legacy has enough efficient removal competition that Glare of Heresy rarely makes the cut outside of dedicated hate packages. Across formats, the card's value scales directly with how much white you expect to face.