This Gruul Eldrazi combo deck wins through the Basking Broodscale/Blade of the Bloodchief loop and almost never casts blue spells, so Mystical Dispute is mostly a generic tax but Engineered Explosives is the real star: set for one, it can blow up Blade of the Bloodchief, Vexing Bauble, or Haywire Mite before the loop starts, and set for two it takes out Basking Broodscale itself. Stern Scolding stays in: it is dead against Devourer of Destiny and Emrakul, but Basking Broodscale and Glaring Fleshraker are both 2/2s it can counter. Preordain, Stock Up, and Beyeen Veil are the trims, since this matchup rewards keeping interaction up over digging and shrinking attackers does little against a combo deck. This is a race where both decks can combo off quickly, so try to be proactive with your own plan while holding Force of Negation and Counterspell to stop Blade of the Bloodchief from resolving. Urza's Saga is a land and its chapter III is a triggered ability, so neither of those can answer it.