Null Rod is a solid but narrower hate piece here. It only shuts off activated abilities of artifacts, so it does nothing to Goblin Welder, Goblin Engineer, or Emry, Lurker of the Loch, which are creatures. What it does hit is a long list of their artifacts: Mox Opal's mana ability, Lotus Petal, Mishra's Bauble, Urza's Bauble, Chromatic Star, Sewer-veillance Cam's sacrifice ability, Skateboard's equip, Legion Extruder, The Filigree Sylex, Agatha's Soul Cauldron's tap ability, and the artifact lands Great Furnace and Seat of the Synod. That slows their mana and disrupts their artifact package. Pithing Needle is the better answer to the creature-based engine: naming Goblin Welder stops its activated ability, which Null Rod cannot do. We cut Chrome Mox since it conflicts with our own Null Rod plan (its mana ability would also be shut off) and we don't want to be down a card against a deck full of cheap, grindy value plays. Lavaspur Boots is low-priority since its equip ability would also be shut off by Null Rod, and this matchup is decided by artifact hate, not combat tricks.