Mono-Black Aggro floods the board with cheap one and two mana creatures like Forsaken Miner and Iridescent Vinelasher, so Slagstorm's 3 damage sweeper is excellent at clearing multiple threats at once. The extra Ghost Vacuum copies help exile problematic graveyard cards, especially shutting down Forsaken Miner's recursion loop before it can return to the battlefield. Get Out's bounce mode is too slow against this aggressive curve, and Spell Snare is weaker since few of their key threats sit exactly at mana value 2. Prioritize sweeping their board and stabilizing behind Eddymurk Crab and Hearth Elemental.