Belcher is a nonland-creature combo deck aiming to Goblin Charbelcher or Sea Gate Restoration for a quick kill, and cheap countermagic is far better than removal spells that have no targets. Consign to Memory efficiently counters their colorless spells like Goblin Charbelcher and Lotus Bloom, while Mystical Dispute counters their many blue spells (Sink into Stupor, Whir of Invention, Waterlogged Teachings) for as little as one mana. Galvanic Discharge and Orim's Chant are largely dead since they have almost no creatures to target and Orim's Chant doesn't stop activated abilities like Goblin Charbelcher, so both are cut. Day's Undoing is risky since it can refill their hand with fresh combo pieces, so it also comes out in favor of proactive counterspells.