Mono Black Aggro floods the board with cheap creatures like Forsaken Miner and Nighthowl Pursuer, so Requiting Hex stays in as premium removal for this matchup since most of their threats are mana value 2 or less, including Gollum, Riddle Master. Dawn's Truce protects your board from removal like Dissection Practice or Shoot the Sheriff by granting hexproof, and with the gift promised it makes your creatures indestructible in combat, buying time for your lifegain engine to stabilize. Get Lost answers an enchantment like Corpses of the Lost that Requiting Hex can't reach, as well as an equipped creature. Emptiness's -1/-1 counters are redundant with your existing removal suite, and Voice of Victory's mobilize tokens only show up tapped and attacking on your turn before being sacrificed, so it can't hold the ground to block their aggressive curve, making it a fine trim.