Holdane, The Betrayer

When Holdane, The Betrayer enters the battlefield, remove the top {x} cards from your
library into your graveyard. This turn only you
may cast one creature from your graveyard
without paying its mana cost.
During your turn, you may cast up to one
creature card from your graveyard.
At the beginning of your end-step, exile one
creature card from your graveyard.