Eldrazi Tron wants to ramp through Urza's Mine/Power Plant/Tower and Eldrazi Temple into Karn, the Great Creator, Ugin, Eye of the Storms, and Devourer of Destiny; Damping Sphere is excellent since their lands routinely tap for 2-3 mana, taxing them down to 1 extra mana and slowing their explosive starts. Metallic Rebuke (cheap via improvise) can counter their big planeswalkers or Devourer of Destiny before it resolves. Vexing Bauble is less impactful here but still answers any free spells; one Pithing Needle, both Claws of Gix, and Shadowspear are cut since they do too little against this grindy, high-mana-value plan.