Postponed Troll

Postponed Troll and the next creature cast enter the battlefield tapped. Postponed Troll doesn't untap during your untap step.
At the beginning of each upkeep, put a +1/+1 counter on each creature that did not untap during the previous untap step.
Whenever a counter is placed on a creature, untap Postponed Troll if it is tapped. Otherwise, tap it.