Gruul Ramp is a creature-based mana ramp deck with big bodies like Jewel Thief, Primordial Pachyderm, and Avenging Hunter, so Breath Weapon's 2 damage is largely ineffective and Relic of Progenitus does little against their non-graveyard-centric plan. Monstrous Emergence lets you snipe their acceleration creatures like Arbor Elf or Jewel Thief, or trade with bigger threats using your own creature's power. Vandalize can strip Wild Growth/Utopia Sprawl-enchanted lands or hit their ramp lands outright, slowing their mana development. Pulse of Murasa buys time and life against their beefy attackers while returning a key land or creature to hand.