Clock Lift

{x},{t}: X target creatures you control gain Flying
until end of turn. Put an hour counter on Clock
Lift. Activate only during your turn.
At the beginning of your upkeep, you may exile a
card from your graveyard. If you do, remove an
hour counter from Clock Lift.
At the beginning of your end step, if Clock Lift
has two or more hour counters on it, exile
Clock Lift.