Jeskai Artifacts relies on small artifact creatures like Emry, Lurker of the Loch, Goblin Welder, and Goblin Engineer alongside combo pieces, so Massacre's -2/-2 wipes most of their key creatures (1/2s and 2/1s) cheaply, and can be cast for free once they have a Plains-equivalent is irrelevant here but the mana cost is cheap regardless. Surgical Extraction is excellent against their graveyard/recursion shells (Goblin Welder loops, Emry mills) by exiling key pieces like Emry or Mishra's Bauble copies outright. Unmask is unnecessary since their deck is mostly artifacts and creatures rather than noncreature spells worth stripping; the extra Koma comes out since its heavy GGUU cost is clunky against their fast combo-artifact plan, though our single mainboard copy stays as a resilient late threat. Keep Thoughtseize to proactively strip their key engine pieces.