Every Last Vestige Shall Rot

Oracle Text

When you set this scheme in motion, you may pay X. If you do, put each nonland permanent target player controls with converted mana cost X or less on the bottom of its owner's library.

Card Rulings

6/15/2010 You choose the target player when the ability triggers. As the ability resolves, you choose a value for X and decide whether to pay . If you do decide to pay , it’s too late for any player to respond since the ability is already in the midst of resolving.