Grixis Affinity floods the board with cheap artifact creatures and burns with Galvanic Blast, so Blue Elemental Blast is excellent both to destroy their red permanents (Myr Enforcer, Refurbished Familiar aren't red, but Krark-Clan Shaman is) and counter their red spells outright. Annul can counter key artifact spells like Ichor Wellspring before they generate card advantage. Cut Abandon Attachments and Spell Pierce, which are too slow against a deck that curves out with zero-mana threats, and trim Ponder slightly to make room since this matchup is about board interaction, not card selection.