Eldrazi Tron is almost entirely colorless spells — Thought-Knot Seer, Devourer of Destiny, Karn, the Great Creator, Ugin, Eye of the Storms, All Is Dust — making Consign to Memory (with replicate for multiples) one of our best sideboard cards. Obsidian Charmaw costs almost nothing since every one of their lands (Urza's Mine, Power Plant, Tower, Eldrazi Temple, Ugin's Labyrinth) produces colorless mana, and its ETB destroying a Tron piece or Eldrazi Temple can outright cripple their mana. Board out Starfield Shepherd, both copies of Thraben Charm, and Witch Enchanter, which don't pressure this matchup enough.