Belcher wants to combo off quickly with Goblin Charbelcher after emptying its library of lands, or ramp hard with Lotus Bloom and Tameshi, Reality Architect bounce loops, so the extra Trinisphere is devastating since it taxes their entire suite of cheap interaction and enablers like Disrupting Shoal, Jwari Disruption, and Preordain. Pithing Needle can name Goblin Charbelcher to turn off their primary kill condition's activated ability entirely. Dismember and two Swamp come out since they field almost no creatures worth killing, making our removal suite largely dead weight in this matchup. Karn, the Great Creator is a premium play here as it can search for Pithing Needle or Trinisphere from the sideboard box after sideboarding, giving us a repeatable way to find our best answer to their combo.