Falnior, Lost to Time

When Falnior, Lost to Time enters the battlefield, tap any number of untapped
creatures you control. For each creature tapped
this way, put a rubble counter Falnior, Lost to
Time.
{t}, Remove a rubble counter from Falnior, Lost
to Time: Add one mana of any color, if Falnior,
Lost to Time has no rubble counters on it,
sacrifice it.