Belcher is a fast combo deck relying on cheap artifacts (like Lotus Bloom) and spells like Whir of Invention and a low curve to assemble Goblin Charbelcher, so Trinisphere is a powerful hate piece that taxes their cheap spells and disruption like Preordain and Spell Snare. Vexing Bauble stops their free interaction such as Disrupting Shoal and any zero-cost effects. Cut Summoner's Pact, which is too risky against a deck that can win before you're able to pay the delayed cost, and trim Malevolent Rumble for more proactive disruption since this matchup rewards taxing their combo over card selection.