Thoughtseize is premium against control, stripping Solitude, Supreme Verdict, or a planeswalker like Teferi, Time Raveler before they can use it to disrupt our plan. Buried Alive telegraphs our graveyard plan and is vulnerable to their Day's Undoing resetting the game, so it comes out for more proactive disruption. Witherbloom Charm is flexible but modest here: it can destroy a nonland permanent with mana value 2 or less like Isochron Scepter (it can't hit Narset, Parter of Veils or Teferi, which cost three), let us sacrifice a permanent to draw two, or gain 5 life to buy time against their removal-heavy shell. Timeline Culler's body is unexciting against a deck planning to Wrath of the Skies or Supreme Verdict the board.