Iterated Onslaught

{t}: Select a creature an opponent controls.
Place a Robusted counter on that creature.
Creatures with Robusted counters on them
are 1/1, have no abilities and cannot be tapped.
Robust counters created using Iterated Onslaught
may be removed by the creature's controller
paying a mana cost equal to the highest power
among creatures you control.