Belcher is a fast combo deck aiming to assemble Goblin Charbelcher off Lotus Bloom and other colorless acceleration, so Consign to Memory is excellent at countering their colorless spells like Lotus Bloom, Goblin Charbelcher, and their triggered abilities. Mystical Dispute is cheap, efficient interaction against their blue spells like Counterspell and Disrupting Shoal that protect their combo. Prismatic Ending is less useful since their key combo pieces are mostly spells rather than permanents worth exiling, so it's trimmed slightly for more countermagic. Keep Thoughtseize maximally in to strip Goblin Charbelcher or key protection spells before they can combo off.