Training montage

Exile target creature and put 3 time counters on it.
At the beginning of your upkeep, remove a time counter from the card. when all the time counters
are gone, put the creature back on to the
battlefield.
For every spell that is cast while the creature is exiled, put one training counter on the creature. when the creature comes back onto the battlefield, it gets
+1/+1 for every training counter on it