Mistakes were made

Whenever an opponent succesfully casts a spell, put a Fate counter on Mistakes were made unless that spell's controller discards a card.
{2}{b}{b}, Sacrifice Mistakes were made: Exile the top X cards of target player's library, where X is twice the amount of Fate counters there were on Mistakes were made.
"I did not bend the knee. I regret my choice every second of my existence." - Grayvan Klenn