Omni-Tell wants to resolve Show and Tell into Omniscience or cheat out Atraxa, Grand Unifier and Emrakul, the Aeons Torn for free, so Chalice of the Void set to zero shuts off Lotus Petal while set to three stops Show and Tell itself, making it a critical hold. Trinisphere taxes their Ponder, Brainstorm, Spell Pierce, and Veil of Summer suite significantly, slowing their combo turn. Ensnaring Bridge is a reasonable speculative add since if they resolve Omniscience without immediate follow-through, it buys additional turns, though your primary game plan should remain proactive lock pieces. Liquimetal Coating lets you turn Omniscience into an artifact target for other removal effects in the deck.