The Preparer

Add the beginning of your end step, look at the
top X cards of your library. Choose up to X
of those cards and exile them face down.
Whenever you draw a card, sum the converted
mana cost of that card with any number of cards
you own in exile. If the total equals the amount
of mana your lands could produce, you may play
the exiled cards this turn.
"You must learn to sail the winds of fortune."