Mono-Blue is a control mirror centered on Phyrexian Dreadnought and card selection, where Smother can target their Dreadnoughts, so it stays in as a low-cost include. Diabolic Edict comes in to answer their 12/12 Dreadnoughts, which matters a lot in a long grindy game. Sickening Dreams is cut since it does little against their high-toughness threat and only hurts your own life total in a matchup decided by card advantage. Lean on your counterspell suite and Accumulated Knowledge to win the long game.