Genesis's Hourglass

{t}: Exile any number of cards in your hand and place four time counters on each of them. At the beginning of each of your upkeeps, remove 1 time counter from all exiled cards. Then, if there are no time counters on an exiled card, for each card without time counters on them, you may play that card without paying its mana cost.
As long as exiled cards have time counters on them, this card does not untap on your untap step.