Mono-Green Eldrazi casts mostly colorless and green spells, and their only creatures that Stern Scolding can hit are Basking Broodscale (2/2) and Haywire Mite (1/1). That is too few targets to justify keeping it in, so it comes out along with Preordain. Mystical Dispute has no blue spells to discount it here, so it costs the full {2}{U} as a soft counter that taxes 3 on one of their key spells. Engineered Explosives is strong because they make a lot of mana value 0 permanents: Eldrazi Spawn tokens from Basking Broodscale and Malevolent Rumble, and Constructs from Urza's Saga. Their small artifacts like Haywire Mite, Blade of the Bloodchief, and Springleaf Drum are mana value 1, so one Explosives can wipe a wide board of tokens and small permanents. It only hits nonland permanents, so Eldrazi Temple and Urza's Saga itself are unaffected. This matchup is a race: their deck is slow outside of Urza's Saga into mana rocks, so assemble your combo as fast as possible and hold Counterspell and Disrupting Shoal (when the mana value lines up) for a Kozilek's Command blowout or an Emrakul, the Promised End. Remember that Emrakul's cast trigger still happens even if the spell is countered. Keep Force of Negation in, but only for their noncreature spells such as Kozilek's Command, Dismember, Ancient Stirrings, and Malevolent Rumble. It cannot counter Emrakul, the Promised End or their other creatures.