Eldrazi Tron is a slow ramp deck relying on Urza's Tron lands, Karn, the Great Creator, and big Eldrazi threats like Ulamog, the Ceaseless Hunger backed by Kozilek's Command, so our combo speed is favored if we can avoid their few proactive answers. Outland Liberator can sacrifice itself to destroy a mana-accelerating artifact like Expedition Map, Talisman of Resilience, or Giant's Boulder, and once it is on its night side its attack trigger punishes any artifact they commit to the board, including Trinisphere. Agatha's Soul Cauldron is a slower, less necessary piece against a deck that is itself trying to go over the top, so we trim it for proactive disruption.