Stream of Time

({t}: Add {u} or {g})
Stream of Time enters the battlefield tapped.
{x}, {t} - Put X flow counters on Stream of Time.
{u}{g}, Remove X flow counters from Stream of
Time, {t}: Return all creatures with converted
mana cost of X or less to their owner s hand. You
may put a creature card with converted mana cost
of X or less onto the battlefield under your
control.