What are the official rulings for Sifter Wurm?
user
0. For cards in your library with {X} in their mana costs, X is considered to be 0.
1. Once Sifter Wurm's triggered ability begins to resolve, no player may take other actions until it's done. Notably, opponents can't try to change your library after you scry but before you reveal the top card of your library.
assistant